THE DETERMINATION OF ACETONE. In the determination of P

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THE

DETERMINATION BY W. M.

(From

OF ACETONE. MARRIOTT.

of Biological Chemistry, the Laboratory University, St. Louis, MO.) (Received

for publication,

September

Washington

4, 1913.)

I Shsffer: this Journal, v, p. 211, 1908. 2 Messinger: Ber. cl. deutsch. them. Gesellsch., xxi, p. 3336, 1888. 3 Lot. cit. 4 Collischonn: Zeitschr. f. anal. Chem., xxix, p. 562. 5 Geelmuyden: Ibid., xxxv, p. 503. 6 Denigb: Ann. Pharm. de Bordeaux, 1910. 7 Scott-Wilson: Jourh. of Physiol., xlii, p. 444. 281

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In the determination of P-oxybutyric acid through oxidation to acetone by the Shaffer bichromate method’ with subsequent estimation of the acetone by Messinger’s iodimetric titration,” difficulty was experienced in obtaining the t,heoretical amount of acetone from known amounts of pure P-oxybutyric acid. It was suspected that either the Messinger titration was inaccurate or that the acetone was incompletely recovered in the distillates. Messinger in his original paper,3 found that in dilute aqueous solutions of acetone, slightly low results were obtained. Collischonn4 found that the Messinger method gave low results in verl dilute acetone solutions. Geelmuyden5 using the Messinger method obtained satisfactory results on purified acetone in aqueous solutions, but found that, on distillation of such solutions, loss of acetone of from 5 to 10 per cent was unavoidable, even when icecooled receivers were used and the solutions were distilled almost t,o dryness. [email protected] claims that the first quarter of the distillate from aqueous acetone solutions contains only about 90 per cent. of the acetone present. In view of the results cited above, it seemed desirable to investigate the accuracy of the Messinger titration and also to determine whether a dilute aqueous acetone solution could be distilled without loss. In addition I have tested the accuracy of the recently described acetone estimation of Scott-Wilson.7

Determination

282

of Acetone

The Messinger method.

Bulb

Bulb Bulb Corr.

I

Bulb

II

and acetone. empty.. ..

.3.1928 .O .7454

Bulb Bulb

andacetone...........2.5939 empty.. . .

.O .9194

for air displacement.

2.4474 .0.0024

Corr.

for air displacement..

1.6745 .0.0017

.2.4498

Acetone..

Acetone.

.

.

.

.1.6762

In measuring out even such dilute solutions as the ones thus prepared, care was necessary in order to obviate loss of acetone. The solution was forced up into the pipette by air pressure from an atomizer bulb, the neck of the flask being closed by a doubleholed rubber stopper. In delivering the solution the pipette was always under the surface of water in the receivingvesse1. In this manner 25-cc. portions of the solutions prepa.red as above, were measured into 700-cc. Florence flasks containing each about 500 cc. of distilled water. A measured amount of standardized iodine solution was then run in, 10 cc. of 60 per cent sodium hydrate added, the flasks stoppered, shaken a little, and allowed to stand for five or ten minutes, after which 15 cc. of concentrated hydrochloric acid were added and the liberated iodine titrated with 8 The bulbs were warmed, and then the t.ips of side tubes acetone, so that on cooling the bulbs acetone rushed in.

dipped

into

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A sample of acetone prepared from the bisulphite compound (Eimer and Amend) was further purified by distillation over potassium permanganate, and redistillation over fused calcium chloride. The product, which was anhydrous and free from aldehyde, was subjected to fractional distillation and two portions collected between 56” and 57°C. Dilute aqueous solutions containing known amounts of this purified acetone were prepared as follows. Thin glass bulbs of 2 or 3 cc. capacity, and provided with a capillary side tube, were blown. These were weighed and then filled with acetone,8 sealed, and again weighed. Each bulb was introduced into a a-liter glass stoppered volumetric flask nearly filled with water. The bulbs were broken under the surface of the water by a sharp blow from a glass rod; distilled water was then added to the mark and the contents thoroughly mixed.

W. M. Marriott standard sodium thiosulphateg results were obtained.

283

in the usual manner. SOLUTION

The following

I.

Iodine solution added 50 cc . . . Thiosulphate.............................................

.

.

.

Iodine used up............................................. Then since 1 cc. of 6 iodine is used up by 0.968 mgm. 30.8X0.968X102.8 per cent=30.64 mgm.’ -4cetone Present by weighing. . . . . .30.62 mgm. i

30.8

of acetone

.

.

.

. (4y.8)

Thiosulphate............................................. Iodine

used up..

. .

.

28.6 .

. .

.

.

21.2

Then 21.2X0.968X102.8 per cent=21.09 mgm. Acetone, Present

by weighing..

The Messinger solutions.

. ..

method,

Distillation

20.95 mgm. :,

then, is accurate

even in quite

dilute

oj acetone from dilute solutions.

It is frequently necessary to distil acetone solutions before making the final determinations. I have found, contrary to the results of Geelmuyden and Denig&s, 10that if proper precautions are taken, acetone may be completely distilled off from even a dilute aqueous solution and entirely recovered in the distillate. Ten minutes’ distillation is sufficient to accomplish this result, as is shown in the following experiment. An acetone solution was used, 500 cc. of which when titrated by the Messinger method were found to contain 33.7 mgm. of acetone. This amount of solution was distilled from an NO-cc. Kjeldahl flask, using a block tin condenser connected with a glass delivery tube, the end of which dipped under the surface of about 50 cc. of water contained in the receiving flask. No ice cooling was used or found to be necessary. Distillations were continued for the length of time indicated, and acetone in the distillates immediately determined by the Messinger method. 9 The thioaulphate was standardized against pure potassium and also against bichromate and found to be 102.8 per cent of &. t.he iodine solution were equivalent to 49.8 cc. of thiosulphate, titrations.

I0 Lot.

cit.

bi-iodate 50 cc. of on blank

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II.

SOL~~TION

Iodine solution added 50 cc.. . .

(*;.8) 19.0

284

Determination Time distilled in minutes

5 10 10 10 15 20 25 30

of Acetone ilcetone distillate

in

27

33.6 33.5 33.7 33.7 33.6 33.7 33.7

Although the Messinger method gives correct results and is the most satisfactory for general use when considerable amounts of acetone are to be determined, yet it is not of sufficient delicacy to determine such small amounts of acetone as occur, for example, in a few cubic centimeters of blood. A more delicate method is that described by Scott-Wilson.” This depends upon the precipitation of acetone as a keto-mercurycyanide compound with subsequent determination of the mercury by titration with a standard sulphocyanate solution under prescribed conditions. In carrying out the method, as described, several difficulties were With certain encountered, and correct results were not obtained. modifications of the procedure, however, I have found the method to be capable of considerable accuracy with exceedingly small quantities of acetone.12 The best results are obtained in the following manner: Dilute soiutions of pure acetone are run into an excess of the recently filtered reagent’3 contained in small Erlenmeyer flasks, allowed to stand __ -.-. ~~ ~I1 Lot. cit. 12 The method is applicable only for quantities of acetone less than five milligrams. 13 The reagent is made up as follows: Mercuric cyanide, 10 grams; Sodium hydroxide, 180 grams; Water, 1200 cc. The solution is agitated in a flask and 400 cc. of a 0.7268 per cent solution of silver nitrate slowly run in. At least 30 cc. of the reagent must be taken for each milligram of acetone present.

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The anomalous results of Geelmuyden and of Deniges may possibly be explained by their failure to always have the end of the delivery tube dip under the surface of the liquid in the receiving flask. The mercury cyanide method of Scott-Wilson.

W. M. Marriott

In the calculation of results Scott-Wilson has assumed that the keto-mercury-cyanide compound has the formula HgCOG(HgCN)4 and that consequently 1 mgm. of mercury should be equivalent to 0.058 mgm. of acetone. He determined the value of the sulphocyanate solution in terms of mercury by titrating it against a known mercury solution. In applying this method to the estimation of pure acetone solutions he obtained results about 3 per cent too low. The error he attributed to loss of acetone by evaporation, or to impurities in the acetone. My results which follow, have led me to believe that the error is instead in the method of calculation. The dilute acetone solution made up from Bulb I, and used as previously described for the Messinger titration was also used in this case. Twenty-five cubic centimeters of this solution were made up to 1 liter with distilled water, and 50 cc. of this latter I4 Filter lz Nitric

paper cannot be used as the strong alkali quickly attacks acid, 40 parts; Sulphuric acid, 5 parts; Water, 55 parts.

it.

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twenty minutes and then filtered through an asbestos maP in a separable bottom Gooch crucible. By first filtering an aqueous suspension of talcum powder so as to partly close the pores of the filter, less difficulty is experiIn some cases the first portions of the enced in obtaining clear filtrates. filtrate are turbid and have to be refiltered. The precipitate is washed with cold water until the washings are free from silver. With the aid of a pointed hooked glass rod the precipitate, mat, and crucible bottom are transferred to a 50-cc. beaker, any adhering particles of the precipitate being washed into the beaker with about 10 ce. of “acid mixture,“‘s 1 cc. off: potassium permanganate is added, the beaker covered with a watch glass, and the liquid boiled until colorless. More permanganate is then added a few drops at a time, until a persistent brown color is obtained which does not disappear on boiling for a couple of minutes. The brown color is then discharged by the addition of a few drops of strong yellow nitric acid. The greater the amount of acetone present the more permanganate is required, and it is essential to the accuracy of the method that an excess be added as indicated above, otherwise the results are low. The beaker is cooled under the tap, 2 cc. of saturated ferric alum added, and a standard solution of potassium sulphocyanate (approximately 0.1 per cent) run in from a burette until a very faint pinkish brown color is The end point, which consists in the obtained throughout the solution. faintest trace of color, can be detected only when the titration is performed on a pure white surface. A control beaker with one drop excess of sulphocyanate should be at hand for comparison. A whole cubic centimeter of sulphocyanate may be run in after the end point is reached without very greatly darkening the shade.

286

Determination

of Acetone

solution, containing 1.53 mgm. acetone, used for each determination. The acetone solutions were each run into 50 cc. of acetone reagent and the estimations carried out as described above. On titration the following results were obtained, and calculations based on the value of the sulphocyanate solution made as indicated. KSCN’” mvn.

cc.

X X X X

0.061............ 0.061......_._... 0.061._....... 0.061............

.

Wm.

1.53 1.53 1.53 1.53

1.44 1.47 1.46 1.44

0.0646 0.0635 0.0637 0.061-S

A second acetone solution was made up from the same stock solution from Bulb I, by diluting 25 cc. of this to 250 cc. with water. Of this latter solution 10 cc.. containing 1.225 mgm. acetone, were used for each determination.

19.2 x 0.061............ 18.6 X 0.061............

1.17 1.13

:

1.225 1.225

1 I

0.0638 0.0658

The results are uniformly low. The figures under the heading “acetone factor” represent the value by which each cubic centimeter of potassium sulphocyanate solution used should be multiplied in order to give correct results for the amount of acetone actually in the solution. The average of these values, which is 0.0644, is then to be taken as the true value of the sulphocyanate solution in terms of acetone. From the foregoing it is evident that the sulphocyanate solution camlot be standardized by its mercury ecmivalent, but that solutions of pure acetone of known strength, as determined by weighing or Messinger titration, can be used to advantage. The discrepancy in the results obtained by using the I6 The KSCN solution was standardized against a solution of mercuric nitrate, that had been analyzed for mercury by sulphide precipitation. 1 cc. of KSCN was found to be equivalent to 1.05 mgm. mercury, which from Scott-Wilson’s formula, would correspond to 0.061 mgm. of acetone.

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23.7 24.1 24.0 23.6

W.

M.

Marriott

mercury equivalent as a basis of calculation may be explained by the possibly incorrect formula for the keto-mercury-cyanide compound or by the reaction not being a complete one. Having thus standardized the sulphocyanate solution: a series of determinations on a different acetone solution was made. The solution used contained 0.172 mgm. of acetone per cubic centimeter, as determined by Messinger titration. Varying amounts of the solution and of acetone reagent were used in order to test the accuracy under different conditions.

2.6t5 2.85 13.40 13.50 27.20 26.80 54.00 54.40

cc. X X X X X x X x

mgm.

0.0644 0.0644 0.0644 0.0644 0.0644 0.0644 0.0644 0.0644

0.170

0.183 0.863 0.869 1.75 1.73 3.48 3.50

mgm. 0.172 0.1'7% 0.860 0.860 1.72 1.72 3.44 3.44

The method? then, gives accurate results with varying amounts of acetone and the accuracy is not affected by considerable amounts of acetone reagent in excess of the quantity required. As previously mentioned it is necessary to use at least 30 cc. of the acetone reagent for each milligram of acetone present, or expected to be present. The acetone reagent is not affected by alcohol, but a precipitate forms with very small amounts of aldehydes, chlorides, hydrogen sulphide, or ammonia. In making determinations, therefore, the absence of these substances must be assured. If the acetone solution is extremely dilute so that several hundred cubic centimeters are required to make a determination, the results have been found to be somewhat low. In such cases it is necessary to distii the acetone into a smaller voIume of water, or better, directly into the acetone reagent. Boiling for ten minutes is sufficient to bring over all of the acetone, and the distillate need not amount to more than 100 cc. The utilization of t’his method in the determination of acetone and of ,&oxybutyric acid in blood and tissues appears in a subsequent paper.

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1

cc. 50 50 50 50 1OQ 100 100 loo

288

Determination

of Acetone

SUMMARY.

1. The Messinger method for acetone estimation gives correct results. 2. The Scott-Wilson method gives accurate results only when It is certain modifications in the original procedure are made. applicable to very minute quantities of acetone. 3. In distilling a very dilute acetone solution, all of the acetone may be collected in the distillate within ten minutes. Downloaded from http://www.jbc.org/ by guest on February 15, 2019

THE DETERMINATION OF ACETONE W. M. Marriott J. Biol. Chem. 1913, 16:281-288.

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THE DETERMINATION OF ACETONE. In the determination of P

THE DETERMINATION BY W. M. (From OF ACETONE. MARRIOTT. of Biological Chemistry, the Laboratory University, St. Louis, MO.) (Received for publicat...

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