16-1
`
`ACIDITY
`
`to form salts,
`their ability to react
`their most outstanding property,
`the molecules react according to the number of replaceable liydrogens of
`acids and hydroxyl groups of bases. Note in the follmving equations
`that
`the reacting powers per mole of HCl, H3804, and HgPOi are in
`the ratio 122:3.
`
`3.1011 + HCI —> NaC‘I + H30
`exuon + 11330, .5 Mesa, + 21130
`3mm + 11,,1’0, ~> more, + 311,0
`
`Hence the complete reaction of one mole of sodium hydroxide requires
`one mole of hydrochloric acid, but only one-half mole of sulfuric or one-
`third mole of phosphoric acid.
`If these amounts of the respective acids
`he diluted to a common volume,
`for example, 1000 ml.,
`the resulting
`solutions are of equivalent concentrations so far as their ability to react
`with alkalics is concerned.
`It is upon such a basis that normal solu-
`tions are prepared.
`By definition a normal solution is of such concentration that one liter
`
`of the solution contains exactly one gram equivalent u‘eight of the solute.
`The gram equivalent weight- is that weight of a compound that contains
`one gram of replaceable [acid] hydrogen, or will react with one gram
`of replaceable hydrogen, or is in any any equivalent to this weight of
`hydrogen. To calculate the gram equivalent weight of acids divide the
`gram molecular weight by the number of replaceable hydrogen atoms
`in the molecule. Since one hydroxyl group requires one acid hydrogen
`for its neutralization,
`it
`follows that
`the gram equivalent weight of
`bases is obtained by dividing the gram molecular weight by the number
`of hydroxyl groups in the molecule. For a salt the divisor is the number
`of liydrogens that have been replaced in the formation of the salt from
`the corresponding acid. Obviously, one obtains a like result in the last
`two instances by dividing the gram molecular weight- by the valence of
`the metal contained therein. Thus the divisor for NaOH is l, but for
`CaSO4 it is 2. The divisor in each case is termed the hydrogen equiva—
`lent. The use of these values in calculations involving normal solutions
`is illustrated in Table 7+1.
`-
`
`frequently
`One gram equivalent weight of a chemical substance is
`called simply an equivalent of that substance. One-thousandth of this
`amount similarly is
`termed a initlieqniualent
`(abbreviation 1n.e.q.),
`which,
`if expressed in milligrams,
`is the same numerical
`figure as an
`equivalent. expressed in grams. For example, in the case of acetic acid
`an equivalent is 60 1:. [Table 7—1) and a milliequivalent is 60 mg. One
`liter of a normal solution always contains one equivalent of the solute,
`one milliliter containing one milliequivalent. Analogous fractions of a
`mole are also frequently used in biochemical work. Thus, one-thousandth
`of a mole is a niiltiinote, and one-millionth is a in-iereniole. Molarit-y
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 164
`
`Petitioner Microsoft Corporation — EX. 1032, p. 164
`
`

`

`.-\CIIJI‘I“1'
`
`10-3
`
`of solutions is indicated by a number followed by .11, and normality
`by a number followed by 3'.
`
`Table 7-l
`
`“Weights of typical reagents in representaliru standard sollllions
`{hint-a or amen-r
`l’r i'lii- r
`P: r ml.
`of iirn'uml
`o} normal
`solution
`solution
`36.5
`0.0305
`00
`[I .1160
`10
`(Hill?
`03
`01163
`75
`01175
`32.7
`0.0327
`6-1
`0.06!
`[U
`0.0 [0
`It?
`0.037
`35
`0.035
`58.5
`0.0595
`130.?
`0.1307
`57
`0.05?
`113.1
`0.1131
`138.1
`0.1881
`8-1
`0081
`
`RE.-\L‘.I-‘.)-'T
`11C]
`HC‘slIst'):
`11:50.
`112C20i‘21120
`112C.Il.0u
`Hal’tli
`II:IC“11.’.():
`NaO H
`[21(011):
`N H4011
`XuCl
`Ball N03):
`' A|2150Ja
`I\-:CJII|OG
`KHCIH.Ou
`NaHCOa
`
`Molecular Myth-nova
`freight
`(“oiiii'rileut
`36.5
`1
`60
`1
`US
`2
`126
`2
`150
`2
`9S
`3
`192
`3
`‘10
`1
`i4
`2
`3:5
`1
`58.5
`1
`261.4
`2
`3-12
`6
`220.2
`2
`188.1
`1
`8-1
`1
`
`It'ouii'olwt
`n'i iylal
`36:)
`[iii
`49
`[i3
`:‘a
`32.7
`5-1
`40
`37
`35
`58.5
`130.7
`37
`113.1
`185.1
`8-1
`
`Standardization of solutions
`
`It. is not always possible to prepare standard solutions by weighing
`out the amount of reagent theoretically required, because many substances
`are not obtainable in sufficient. purity, and others take up water or
`carbon dioxide when exposed to the air during the time required for weigh-
`ing. Solutions of such substances can, however, be “standardized” by
`titration against a solution of known concentration prepared from a.
`“primary standard,” that is, a substance that can be obtained in a high
`state of purity and conveniently weighed.
`l-‘requcntly, normal solutions
`are too concentrated for accurate measurement of the limited amount
`
`In general prac-
`
`of acid or base in the substance that is being analyzed.
`tiee, 0.1 normal solutions are quite satisfactory.
`Titration is a process of measuring the volume of one solution that is
`required to react exactly with a definite amount- of :1. second solution.
`In titrating acids and bases the point. at. which the reaction is completed
`is revealed by the color of an “indicator," which is. added before the
`titration is started. The selection of a suitable indicator is explained
`below.
`In practical work equal volumes of solutions of
`the some
`normality are considered to react exactly with one. another.
`If the two
`solutions do not have the same normality, it takes proportionately more
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 165
`
`Petitioner‘Microsoft Corporation — EX. 1032, p. 165
`
`

`

`166
`
`ACIDI‘I‘Y
`
`of the less eoneenti‘atcd to titl‘ate a given quantity of the more concen-
`trated.
`If solution A is tit-rated against solution It, the following rela-
`tionship holds:
`
`Volume of A X normality of .1 = volume of It X normality of B
`
`'l‘llus if the normality of A is known. that of B may be. calculated from
`the titration data, since from the ahove equation it may be seen that
`
`volume of .\ X normality of .-\
`-
`normalitr of l'. ‘--
`\‘olllme of 15
`‘
`
`As an example of a typical stamlardiaation let us assume that 21.4
`ml. of a solution of sodium hydroxide are required to neutralize 25 ml.
`of tenth-normal {0.1.\') oxalic acid. The normality of the sodium hy-
`droxide solution will then he equal to
`23 X [1.1
`21:, : 0.11.1r
`
`that. the sodium hydroxide solution is 0.1]?
`We should say. therefore,
`normal, which means simply that. it is 0.117 times as concentrated as a
`normal solution.
`It is obvious that if solution A is one-tenth as concentrated as solution
`
`that. 1.‘olumc of
`to one-tenth of
`B, a given volume of A is equivalent
`B. Likewise in the example just. considered, 1000 in]. of the, solution
`that. is 0.117 normal
`is equivalent.
`to only 11? ml. of normal solution.
`The rotume of a solution. used in o titration. a'hcn iiudti'plicd by its
`normality gives the cquimlrnt
`rota-ine- of normal solution.
`In other
`words, by means of this calculation one determines the volume that
`the solution would occupy if it. were exactly normal.
`
`Analysis of biological mt'uerial's
`
`In order to determine the percentage of a given constituent in an)r
`material, two things must be known, namely, the weight of sample taken
`and the amount of standard solution needed to titrarc it. The follow-
`
`ing calculation of the citric acid content. of lemon juice is typical:
`
`Weight. of sample ..........................................
`Volume of alkali, normality 0.103. for titration ..............
`l'tIoleculnr weight. of citric acid (H3C011507) ..................
`Hydrogen equivalent, of citric acid ..........................
`Equivalent weight of citric acid .............................
`Weight. of citric. acid per ml. of normal reagent ______________
`Volume of normal citric acid equivalent
`to alkali used for
`titration (3-1.6 X 0.103) ..................................
`Weight. of citric acid in sample (3.55 X 0.064) ................
`9..
`
`5.0 g.
`34.6 ml.
`192
`3
`61
`0.064 g.
`
`3.50 ml.
`0.2278 g.
`
`Coneentmtion of acid in the. juice (w) ........
`
`4.56 per cent.
`
`Petitioner Microsoft Corporation — EX. 1032, p. 166
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 166
`
`

`

`ACIDITY
`
`167
`
`Indicators
`
`The ability to determine when sufficient. reagent has been added in
`titration of an acid or base depends upon the sensitivity of certain dyes
`to changes in acidity.
`b'uch compounds are called indicators. Many
`dyes that are used as indicators change color in either slightly acidic.
`or basic media rather than at exact neutrality. This:
`is a desirable
`charm'tcristic, as may be seen by a study of the salts formed through
`interaction of
`the.
`respective acids and bases. Salts of strong bases
`and weak acids, e.g., sodium carbonate, undergo hydrolysis when (lis—
`solt‘ed in water, producing basic solutions, whereas those salts. formed
`by union of weak bases and strong acids.
`like :nnmonium sulfate, are
`somewhat acidic for a similar reason.
`'i‘lleretol‘e when titl‘ating an acid
`with a base, or vice versa,
`it is essential that the standard solution be
`added until
`the same degree of acidity or alkalinity is produced that
`would result by dissolving the corresponding salt
`in water. Choice of
`indicators is made accordingly rather than with the idea of determining
`the point of exact neutrality. Methyl orange, methyl red, bromtbymol
`blue, and phenolphtlralein are examples of indicators in common use.
`The first two are suitable for titration of weak bases, and the last one
`for weak acids.
`
`HYDROGEN-ION CONCENTRATION
`
`”Active” acidity as contrasted to “total” acidity is due solely to that.
`portion of the total replaceable hydrogen that, under prevailing condi-
`tions, exists in the ionic state. As a commonplace illustration one may
`liken acidity of a solution to the wealth of an individual.
`'l‘otal acidity
`corresponds to total wealth, which includes currency, real estate, personal
`property, notes, bonds, and so on. Active acidity, on the other hand,
`is comparable only to currency, and just as the response of a. ticket sales-
`man is conditioned by the currency in the hand of a prospective pur-
`chaser, so the behavior of a cell
`is conditioned by the active hydrogen
`in the aqueous medium surrounding it.
`It.
`is true that other forms of
`wealth are. convertible into currency, and,
`likewise, acids tend to dis-
`sociate further as some of their hydrogen ions are used up by chemical
`reaction.
`
`to do with enzyme
`The hydrogen-ion cmicent-ration has much more.
`act-ion and the maintenance of a normal colloidal structure.
`in cells than
`
`A fatigued muscle may contain as much as 0.4-0.5
`has total acidity.
`per cent
`lactic acid for a time without undergoing injury, but a like
`concentration of hydrochloric or sulfuric acid would result in death to
`the tissue. Consider also the supply of carbon dioxides—potentially car-
`bonic acid—carried by the. blood stream.
`Introduction into the blood
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 167
`
`Petitioner Microsoft Corporation — EX. 1032, p. 167
`
`

`

`163
`
`ACIDITY
`
`stream of an equivalent amount of other common acids, even such acids
`as citric and acetic, which the body normally oxidizes for energy, would
`doubtless be fatal.
`In these two instances it,
`is not the concentration
`
`is the
`it
`injury results;
`of total acid that determines whether or not
`concentration of hydrogen ions. Figure -?—2 shows the effect of various
`ll_\‘lll‘:i;_‘;t‘I]—inn concentrations on plants. Growth is poor when the active
`acidity is too high [pH too low).
`
` 4’,» «(70‘5“
`
`(.‘nurtesy of Illinois .\:.’I‘l('ultlll‘.'ll Experiment Station. Reproduced from Humm-
`ution of
`the American Society of Agronomy and the
`Signs in (Tops,
`.'1 put]!
`National Fertilizer As.
`.ntinn, Washington, I). ('.
`
`Fig. 7—2. The effect of increasing acidity (left to right) on growth of red
`clover. The poor growth results from calcium starvation, because high
`acidity interferes with the absorption and retention of calcium by the plant
`roots.
`
`For these reasons measurement of the hydrogen-ion concentration fre-
`quently is of more significance than determination of titratable acidity
`or alkalinity of a given biological fluid or extract. But one must not
`conclude that active acidity is always of prime importance. A familiar
`illustration involves the use of soda and sour milk as a leavening agent
`in the making of corn bread.
`If the housewife should add only enough
`soda to react with the hydrogen ions initially present in the sour milk,
`most of the lactic acid, i.c., the nonioniacd part, would not be neutralized,
`and sour bread would be the inevitable result. Sufficient soda to react
`with all of the acid must be added.
`
`Water is a neutral substance because it yields an equal, though rela-
`tively small, number of hydrogen and hydroxyl
`ions. The concentra-
`tion is lmown to he 0.0000001 [also expressed 10—7) gram-ion per liter,
`which is equivalent to 0.0000001 g. of hydrogen ions and 0.0000017 g. of
`hydroxyl ions.
`It must be borne in mind that hydrogen ions exist even
`in basic solutions. Their concentration is reduced as basicity increases,
`but, theoretically, all are never entirely removed from a solution.
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 168
`
`Petitioner Microsoft Corporation — EX. 1032, p. 168
`
`

`

`manrrv
`
`| 0')
`
`Cont-entration of hydrogen ions may he expressed direetly in gram—ions
`per liter as above {eolnlnll'alile to moles per liter when eoiisiderinu a
`given reagentl. Usually, however, when dealing with biologieal ma—
`terials this neeessitates the use of relatively reinall deeimal
`fraeliom
`with attendant possibility of an error in writing.
`.-\ more eonvenient
`method is that of pit, 11y which one merely expresses the logarithm of
`the reeiproeal of the hydrogen-ion emn'entration. Thus the reeiproeal
`of 0.0000001, the hydrogen-ion eoneentration of water,
`is
`]0,000.000 or
`107, and the logarithm of this number is 7. The pll of pure water there—
`fore is 7, and all solutions of sneh pI-I are said to he neutral.
`in view
`That- aeidic solutions have pH values less than 7 is apparent
`of the feet that any concentration greater than 0.0000001 will have .1
`eorrespondingly smaller reeiproeal and eonset'iuently a Smaller lonaritlna
`lplI valuel. Conversely, all hasie Solutions have pll values greater than
`7. To those unfamiliar with this systen‘u of expressing aetive avidity,
`it may seem that. small dili'erenees in pll eorrespond to unbelievably areal
`differenees in aetual
`liydrom-n-ion eoneentmtion. This van best
`1):'
`realized by a eomparismn of several hydrogen-ion eoneentratiom and
`corresponding pH values simultaneously:
`
`(‘oneenfmtion in
`gram-ions per liter
`0.1
`0.001
`0.000001
`0.0000000]
`00000000001
`
`h’eeipmenl of
`emu-entrain)”.
`10
`1.000
`1,000,000
`100.000.0110
`10.000.000.000
`
`pH
`1
`3
`0
`8
`10
`
`Thus far only a tenfold (or some, power thereof) increase or deerease
`in hydrogen-ion concentration has been considered,
`lmt
`it
`is olJvioto:
`that between any two sueh values, e.g.. {1.1 and 0.01 gram-ions per liter.
`are countless possible Concentrations with corresponding pH values. To
`make interpretation of pH values easy Table. 7—2 has been inelurled.
`Column 1 merely gives. the approximate logarithms of some appropriate
`numbers between 1 and 10 {listed in column 2).
`
`Table 7—2
`
`Comparison of pH values
`
`Change in pH
`0.1
`.........................................
`_
`_
`0.2 ........................................
`.
`.
`.
`0.3
`..................................... .. .
`_
`.
`.
`.
`0.6
`.........................................
`0.9 .................................................
`1.0 .................................................
`
`..
`.
`.
`
`Approximate equivalent
`ehenoe m Heidi-1y
`1.25 times
`[,6 times
`2.0 timer:
`4.0 times
`8.0 times
`10.0 times
`
`.
`
`.
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 169
`
`Petitioner Microsoft Corporation — EX. 1032, p. 169
`
`

`

`170
`
`ACIDI‘I‘Y
`
`Example. Compare pH 6.6 and 5.1.
`The difference between pH 6.6 and 5.1 is 1.5 units, which can be. broken down into
`units found in the table, namely. 1.0, 0,3, and 0.2.
`
`times.
`A difference of 1.0 equals 10
`'times.
`A difference of 0.3 equals
`'3
`A {liiTI’I'E’Ilt'l' of 02 equals
`1.6 times.
`Hence a difference of 1.5 equals 10 X 2 X 1.6 = 32.
`Therefore. pH 5.1 is 321imesasaeid as pH 6.6.
`
`Buflcrs
`
`Although addition of a minute amount. of hydrochloric acid, or any
`other strong acid,
`to water produces relatively a great change in pll,
`biological fluids.
`in general, do not undergo a eoniparahlc change when
`strong acid or base is added to them, because of the presence of certain
`compounds in these fluids.
`tiuch compounds which resist change in
`acidity or basicity are known as buffers.
`In general, a butter consists of a weak acid [or base) and its salt.
`The buffer is the noirtio'c of the two substances. Examples are acetic
`acid—sodium acetate, carbonic acid—sodium bicarbonate, ammonium
`lly'til'flxidflw-fllilnltinlllln chloride. Frequently the second hydrogen of a
`di- or tri-basie acid serves as the weak acid, as in the butter NaIIgl’th—
`NagHPCh. Other metals, such as potassium, are equally satisfactory
`in butters provided they form water-soluble salts with the acids concerned.
`Buffers exert their ell'ect through chemical reactions that use up most
`of the hydrogen or hydroxyl ions that are added. This action depends,
`fundamentally, on the fact that the weak acid {or base) is only slightly
`ionized. A weak acid [IA ionizes according to the equation:
`
`ILLF’ II+ + A*
`
`The A— here represents the acid radical. Since this ionization is a
`reversible process, the addition of extra hydrogen ions shifts the reaction
`back to the left
`(law of mass action] and thereby converts most of
`the added H+ into undissociated 11A molecules. 0n the other hand, if
`a strong base is added to the buffer, the 011* ions r ‘act with ll+ to form
`water, and more of the IL! molecules ionizc to replace most of the H+
`ions used.
`In either case the 1:11 remains relatively constant.
`The exact pH of any individual bufl‘er solution and the pH change
`resulting from the addition to it of a certain quantity of strong acid
`or alkali may be calculated readily from a knowledge of the dissociation
`constant of the weak acid or base in the buffer. The mathematical
`
`expression for the dissociation constant K, of a weak acid is based on the
`equation for its ionization.
`It. is:
`
`K : [H+] ' [A‘]
`a
`[as]
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 170
`
`Petitioner Microsoft Corporation — EX. 1032, p. 170
`
`

`

`acun'rr
`
`171
`
`Since.
`The brackets indicate concentrations expressed on a molar hasis.
`weak acids ionize to only a slight degree, the numerical values oil “4'1
`and [.\—j are small, whereas 111A]
`is large.
`(.‘oilsequently Kn for Wen];
`acids is a sum“ number,
`for examplc,
`titltllJUlb‘
`in the ease of acetic.
`acid. The weaker the acid. the smaller is its A}. value, and vice versa.
`
`Htrotlg aeitls like hydrochloric are considered to lJl’ completely ionized
`in water solution and, therefore, have no, or more exactly an infinitely
`large, Kn value.
`Considerations exactly similar to those set forth above apply also to
`weak bases. The corresponding expressions are:
`11011: 13+ + 011‘
`
`and
`
`To illustrate how p11 values of particular buffers may be calculated,
`several typical problems will he Worked out.
`
`PItUBlJ-ZM 1. What i.“- the [ill of a 0.1.1! acetate trailer solution?
`The. phrase "0.1.11 acetate buffer" means that both acclic acid and sodiun;
`acetate are. present in 0.1.11 concentration. The ionization equation for acetic
`acid is:
`
`CH3C00H 3211+ + C113COO“
`
`and its dissociation constant has the numerical value 1.8 X 10—5.
`he found from the expression for tlte dissociation (‘Ollelilllll
`
`The. 1111 Ina):
`
`K" = 1.8 x10": 2
`
`[11+i-|C1L,eoo—]
`[L‘II;,C‘0tllI|
`
`by inserting the proper values for [CH3C‘OO—] and [CllgCODtI], and solving
`for [H+].
`Let X: [11*]. Then [CilaCOOII] : [0.1—X], since the original acetic
`acid concentration was 0.111. The concentration of acetate ions is
`the sum
`of the concentrations t‘esttltinflrtr from the ionization of laotli acetic. acid and sodium
`acetate. That
`from the acetic acid is. obviously X, while that
`front sodium
`acetate is 0.1, because such salts are strong electrolytes and are completely ionized
`in aqueous solution. Therefore, [CH-1000‘] = Q1 -1— X).
`Substituting these values in the expression for K; we have:
`X ' {0.1 + X1
`
`1.8 X 10—5 :
`
`{0.1 — X}
`
`New X is very much smaller than 0.1, since we are dealing with a slightly
`ionized acid, so {0.1+.\') and (0.1 —J.'] are both very ncarly equal
`to 0.1.
`Making this substitution, we have as :1 close approximation:
`0.1x
`‘7' = ———
`.S
`{H
`1 X 10
`X 21.8 X 10—5
`
`or
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 171
`
`Petitioner Microsoft Corporation — EX. 1032, p. 171
`
`

`

`172
`
`acroirr
`
`Since the pH is the negative logarithm 1 of the molar H+ concentration,
`
`pH : — log [1.8 X 10““)
`— log 1.8 +(—log10—5)
`— 026 + 5
`4.174
`{Answer to Problem 1)
`
`llIIIt
`
`Note that in this problem [H't] : Km or pH =pKa. This relation
`holds for any butler where the acid and salt are present in equal amounts.
`When different amounts are present,
`the 1111 may be calculated from
`the equation:
`
`[acid]
`'1' 2 '
`..___.
`]
`A... x [salt]
`
`[11
`
`In the case. of a base-type butter, the. corresponding equation is:
`
`1base]
`_ _ ,
`[OH ]#RUX [salt]
`
`If the. composition of the buffer and the numerical value of Kl. are known,
`[OH—j and, hence, pOH can be calculated. From this result the cor—
`responding pH value can easily be found from the relation:
`
`pH + DOH = 14
`
`which holds for any aqueous solution at room temperature.
`The use of the above equations in buffer calculations is illustrated
`below.
`
`PROBLEM 2. What is the p11 of 40 ml. of 0.1Mr acetate boiler to which has
`IJDCII added 10 ml. of (MN IICl?
`
`The IlCl added amounts to 1 m.c.q. (10 X 0.1), and the buffer originally con-
`tained 4 ni.e.q. (40 X 0.1) each of acetic acid and sodium acetate. For purposes
`of calculation it may be assumed that the 1 men. of HCl reacts with 1 m.c.q.
`of sodium acetate to form 1 m.e.q. of additional acetic acid”:
`
`HCl + CI13COONa—> NaCl + CHaCOOH
`
`(£13.:
`Consequently, the acid :salt ratio of the butler has been changed from 1
`4 : 4) to 5 : 3. The pH may therefore be calculated by substituting known values
`in the equation above:
`
`[H+] =13 X10—5 ><—53
`:— 3 X 10—5
`pH 2 4.52
`{Answer to Problem 2)
`
`whence
`
`“rho small letter “p" is used to mean “the negative. logarithm of."
`21101-9 precisely. since the ROI. NaCl. and L‘IlaCOONo do not exist as such in
`water solution but are IOU per cent
`ionized at all
`times.
`the only reaction which
`actually occurs is:
`
`11* + CIl,L‘-OO'—) CIIEUOOH
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 172
`
`Petitioner Microsoft Corporation — EX. 1032, p. 172
`
`

`

`.-\t:II)1TY
`
`175’)
`
`the boiler has dropped only (1'23 unit. This
`the original pll of
`Note that
`answer sliows very clearly the effect of the buffer because if 10 III]. of (LIX H('|
`are added to 4t] 1111. of plain water, without any lth-r present, the resulting ll
`concentration is
`l m.e.q.
`in :30 ml, or 0.02.11.
`'l'lu-rel‘orc the pit is —log 0.02,
`or I}, a very much greater drop.
`
`The. salt-acid combination is most effective when the salt and acid are
`
`present in equal molecular proportions. Of course. there is a limit to the
`capacity of the buffer to take up hydrochloric acid or sodium hydroxide.
`For example, when about 85 per cent of the sodium acetate has been
`converted into acetic acid, or rice versa, the limit is close at hand.
`{in
`adding more acid or alkali, the pll of the solution changes rapidly, and.
`hence, there is little buffer action.
`
`The most widely used buffers are mixtures of sodium or potassium salts
`of relatively weak acids and the corresponding free acid. For most
`purposes, acids such as phosphoric,
`'arbonic, acetic, and other organic
`acids are. used. Carbonates, hiearbonates, and phosphates.
`together
`with proteins, form the most important buffers in the body.
`'l‘hese main-
`tain the pH within very narrow limits even though considerable acid or
`base is added.
`
`Measurement of pH
`
`Each hydrogen ion bears an electric charge, and the concentration of
`these ions can be measured most. accurately by clcetrometric means.
`This method, however, requires the use of relatively expensive apparatus
`and an experienced operator. For many dyes there is a particular degree
`of acidity at which there is a very definite change in color, and fortu-
`nately the various dyes, or indicators, change color at differenthydrogen-
`ion'coneentrations. This fact serves as a basis for a cohn‘imetric method
`
`that is quite simple, as well as fairly accurate. The method consists of
`matching the color produced by an appropriate indicator in the unknown
`solution with the color of a standard solution of known hydrogen-ion
`concentration to which the same indicator has been added.
`If the color
`
`of the unknown is the same as that of the standard, the hydrogen-ion
`concentration likewise must be the same. Standard color charts and
`
`glass discs of appropriate colors that may be substituted for the standard
`solutions possess the added advantage of being more perinancnt
`than
`the solutions.
`
`In Table 7—3 are given the approximate pH values of a number of
`biological materials.
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 173
`
`Petitioner Microsoft Corporation — EX. 1032, p. 173
`
`

`

`174
`
`ACIDITY
`
`7.0
`7.8
`5.5
`7.0-3.0
`6.1—6.8
`1.5-2.4
`8—9
`
`Table 7—3.
`pH values of representative biological maleriafls
`pH l'alur
`Material
`Blood, normal
`limits ................................... 73-75
`Blood, extreme limitx ...................................
`T.0—7.S
`Enzymes. activity range of
`Aniylopsin, optimum ................................
`l'hmisin. optimum ._
`...............................
`IIH‘l'l'lqu‘. optimum ..................................
`Lipase.pancreatic....
`Maltase, optimum .....................................
`l’epsin, optimum ......................................
`'l‘n'psin. optimum .....................................
`Fruit juices
`3.8
`Appli- .................................................
`4.6
`Banana ...............................................
`3.0-3.3
`Grapefruit.
`............................................
`3.1—4.1
`Orange
`Tomato 4.2
`Gas-trio juice, adult. ......................................
`1.6—1.8
`Milk. cows. limits .
`....................................
`6.24.3
`Milk. human ..........................................
`7.0—7.2
`Must-Iv juire
`.
`.
`. .....................................
`6.8
`Plants (extracted juice}
`'
`59
`Alfalfatoprs
`5.2
`Carrot ...............................................
`Cucumber 5.1
`Peas, field .............................................
`6.3
`Potato ................................................
`6.1
`Rhubarb; stalks _______________________________________
`3.4
`String beans ...........................................
`5.2
`Saliva
`..................................................
`6.2—7.6
`Sweat ...................................................
`4 .5—7 .1
`Team .....................................
`7.2
`Urine. human, 11mm- 4.2-8.0
`
`REVIEW QUESTIONS ON ACIDITY
`
`In what
`
`1. Explain the difi'ereni-e in meaning of “active” and ”total" acidity.
`terms are concentrations of the two usually expressed?
`2. Define:
`(1) molar solution,
`(‘2) normal mllllioin (3) hydrogen equivalent, (4)
`gram equiValent wright, (5) lllllll'fllol'.
`3. What is the normality of a solution of NaOH if 25 ml. of it are required to
`neutralize 20 ml. of (LIN oxalic acid?
`4. What. is the normality of a solution of noel-ii- al-iil which contains 0.3 g. of this
`reagent in 50 ml.?
`5. “(but volume. of U.5.-'\" NaOH would lJO required to neutralize the acetic acid
`mentioned in the preceding question?
`6. What is :1 hydrogen ion‘iI Represent by equations the ionization of (l) HNOa.
`(2) NaCl, (3) CILL‘HOHCOOH, (4) 373011, (5) 11380;.
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 174
`
`Petitioner Microsoft Corporation — EX. 1032, p. 174
`
`

`

`Mtlnrn'
`
`175
`
`\Yl'itt- i‘quutimls tn i1111:~lr:tll‘
`:1 Inlsz-r'.’
`7. “11:11. 1r:
`”(‘1 “ml NuUH. I'vslu-(‘lit'vl_\'_
`S. What do lull 5. 7.:1Ii-191nvnli with roam-1 In :Lrislily. Ill'llil':iiil_\'. :Imi alkalinity?
`9. How lulu-1| mul'r‘ :u-iii is [lu- first
`lllt‘lllin'f‘ :11" tin- following puil‘fi than Ilw sm-nncl
`nll‘llllll‘l': pll 6 vs. T. 1111
`l\'.~'.‘.'.|111 1.2 vs. (5.3. pll
`IV». 5.3. 1.11 2 \'.-u. 111'?
`ll]. Ciivr.‘
`[1w umnmximntt- 5:11 \‘uluc-s of six ru-lnrz-n-nlnliw Jniulngis-ul
`In:|h‘1'i;tl:~..
`ll. Giro tlm mum's :iTlll r-tl‘lll'l'lll‘s'li formulas of Ion orgunil- :u-inis (other than fully
`uridn‘) “.1111 fire orgn‘nit'
`lut-‘II-r- commonly found in hinitigil'ni
`:11:I1I'l‘i:II:-‘.
`
`thl- rI-:1(.'I.im1 (11'
`
`:I buffl'r with
`
`REFERENCES AND SUGGESTED READINGS‘
`
`l‘u-ss. Inna. Xvw York, 1950.
`Bonnm‘. erms, tht Bfurhrmi'srry. A(‘Illil'lnil'
`Clark,
`‘1", 31.. Th: Urhrmirmtimr ”I Hytia'nfnr'r 1mm. 3H1 £11., Tim \Yillir‘lllls and
`Wilkins Column}: linliin'mro. 1928.
`Kolthol‘f, I. M. uml Luil'im-n. ll. .-\__. pH mu! Ehr‘trntitmtiun.~;_ 21:11 (‘11.. John “‘ilt‘)‘
`and 1350115. Inn. New York. 19-11.
`11:1 Mottt‘. 1“. Lu Kenny. “I. 1L.
`:1an Rr'l'ti. A. 1%.. pH and H»: Frantic-(IE .‘ippiirntfon,
`Tlu» “1111-11115 and Wilkins Company. Hullilllm'l'. 1932.
`l’it‘rrv. W. C. and 1'1:ll‘Ili.-'l'il, E. 11., (Jurmhfmh'm- Analyst's. 3rd OIL. John “110'
`Suns, lmn, New York.
`11'! IS.
`Schmidt. C. L. A. and Allen. 1:. \Y,, Fmrriumr with of Hindu mwm. 151 ML. 110(1111W-
`Hill Book Compuny. 111:2. Xl'w York. 1938.
`
`:iml
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 175
`
`Petitioner Microsoft Corporation — EX. 1032, p. 175
`
`

`

`Chapter 8
`
`BIOCHEM ICALLY IMPORTANT MINERAL
`
`ELEMENTS
`
`Definition
`
`The mineral elements of biochemical
`
`interest are all
`
`those chemical
`
`elements, except carbon, hydrogen, oxygen, and nitrogen. which are, or
`may be, present. in the tissues of living organisms. They are frequently
`called inorganic. or ash elements, since. as a rule,
`they remain in tl:e
`ash when biological materials are burned. Those which have. been
`proved to be essential constituents of
`living tissues are listed below.
`The? are classified as major and minor (or trace) elements on the basis
`of the. amounts usually present in biological samples.
`Mama MINI-1am ELEMENTS
`
`.11: tats
`Sodium
`Potassium
`Calcium
`Magnesium
`
`.\'omuctois
`Sulfur
`(.‘hlorine
`Phosphorus
`
`' Mixon )IIXEIHL ”£3”:sz on TRACE ELEMENTS
`
`.Yui‘mu‘tuis
`Iodine
`Boron
`
`Ah fall's
`Iron
`Copper
`Co halt
`Zine
`Manganese
`i\'Iolyl.idenuin
`
`Most of these elements are. required by living organisms, generally.
`However, boron is needed only by plants; sodium, chlorine, iodine, and
`cobalt, only by animals. Thus plants require 15 chemical elements in
`all [counting C, H, 0, and Ni, and animals 18.
`Aluminum, vanadium, arsenic, bromine,
`fluorine, silicon, and other
`mineral elements are widely distributed in living cells and may have.
`important biological functions, but as get their essential nature has not
`been demonstrated, ('Xcopt
`in a few isolated cases
`(e.g., vanadium is
`apparently a normal, necessary constituent of a respiratory pigment- in
`lit:
`
`Petitioner Microsoft Corporation - Ex. 1032, p. 176
`
`Petitioner Microsoft Corporation — EX. 1032, p. 176
`
`

`

`lthCllEMlC.-\l.l.'t'
`
`I.\IPUItT.-\N'l‘ MINERAL ISI.I'I.\II'II\"I‘S
`
`17?
`
`certain marine \vormsi. Still other clean-Ins. for example, selenium. are
`found only in the tissues of plants or animals crown in certain restricted
`localities. Some of these elements which are of interest
`for one reason
`or another are. discussed in more detail below.
`
`Asking
`
`When it is desired to examine a biological sample for mineral elements,
`the first step is to dry the sample, then burn it to remove organic matter,
`and convert
`the mineral elements present
`into simple inorganic com-
`pounds. From the chemical standpoint the process of burningr or ashing
`is essentially a very vigorous oxidation, which is carried out
`in the air
`at. a temperature of about UUO~SOO_C. The organic substances present.
`are decomposed as the sample is heated and turn black on account of the
`formation of free carbon. As the heating continues this carbon is oxi-
`dized to carbon dioxide. which esmpes. Disappearance of
`the black
`color, therefore, indicates that the ashing is complete. The hydrogen in
`the original m'ganic matter is converted to water vapor. and the nitrogen
`escapes in the. form of nitrogen gas.
`The mineral elements are contained in biological materials partly in
`complex organic combinations such as sulfur in methionine, phosphorus
`in lecithin, iron in hemoglobin, etc.
`(see. Table 8—2}. As these.
`tn'gflnip
`substances are destroyed during the ashing process, the mineral elements
`in them combine with .‘aeh other——metals with nonmetals—and fre-
`
`out-ntly also with oxygen to form inorganic salts such as the chlorides.
`sulfates. phosphatt.-s and silicates of sodium, potassium. calcium, and
`magnesium. The ash, then, consists largely of these salts.
`If the sample happens to contain relatively more metals than non-
`metals, as in vegetables, fruits, milk, only a part of the metals present
`can be converted into such salts because there will not- be. enough
`nonmetals to go around.
`In this case the excess metals combine with
`oxygen or car