Practical organic and bio-chemistry / by R.H.A. Plimmer.

  • Robert Plimmer
Date:
1915
Catalogue details

Licence: Public Domain Mark

Credit: Practical organic and bio-chemistry / by R.H.A. Plimmer. Source: Wellcome Collection.

    613/660 page 593
    The acetone distils from the first flask, is freed from phenol and volatile organic acids by passing through the caustic alkali and is precipitated in the receiver as keto-mercury compound. The distillation is continued for 5 minutes after the first appearance of a turbidity in the receiver. When the heating is discontinued the glass rod is removed from the rubber piece of tubing so as to prevent back suction of the liquids. The adapter is discon- nected, rinsed out, and the precipitation is allowed to SombIete itself by standing for 10 minutes. The precipitate is filtered off through a thick filter paper or asbestos mat in a Gooch crucible, the pores of which have been closed by first filtering an aqueous solution of talcum. The. first runnings, if turbid, must be passed through the filter again until a clear filtrate 1s obtained. The flask and pre- cipitate are washed with distilled water until the washings are free from silver. The precipitate together with the filter paper or asbestos mat are transferred from the crucible by means of a pointed glass hook to a clean flask or beaker and any particles adhering to the crucible or hook are washed in with a jet of acid mixture. More acid mixture is added so that the volume used altogether is about 10 c.c. 1 c.c. of ‘2N potassium permanganate solution is added and the contents of the flask boiled for 1-2 minutes till they are colourless. It is better to add a few drops of permanganate during the boiling so that a persistent brown colour is present and to decolorise by adding a few drops of strong yellow nitric acid. The contents of the flask are cooled and titrated with ‘1N thiocyanate solution? (about ‘1 per cent. KSCN; 1 c.c.=1 mg. Hg), using 2 c.c. of saturated ferric alum solution as indicator until a brownish tinge appears. A control beaker containing 1 drop excess of thiocyanate should be at hand for comparison. 1 c.c. ‘IN KSCN = ‘oor gm, Hg = ‘0058 gm. acetone (Scott- Wilson). es 5 = *00644 3 (Marrictt). Micro Analysts. The above methods are not suitable for the estimation of the acetone and aceto-acetic acid in small amounts of blood, but the Scott-Wilson method can be adapted to the estimation of 0°2-0’5 mgm. acetone as shown by Marriott. With such small quantities of acetone the reagent gives a turbidity which can be,compared in a nephelometer with the turbidity given by a standard acetone solution containing *5 mgm. Folin and Denis #4 find that the turbidity comparisons can be made with a Duboscq colori- meter thus avoiding the use of the nephelometer. . The colorimeter must be carefully adjusted to the light so that the two fields are perfectly alike when a standard suspension is read against itself. It is preferable to have the light coming through a hole in a dark (green) window shade so _ as to exclude the interference of more or less bright objects. In mixing the solutions in which the suspensions are formed they must not be shaken, but only gently rotated or inverted. The procedure of Folin and Denis with small quantities of urine can be adapted to the estimation in blood, following Marriott’s preliminary treat- ment to remove the proteins :— The air current method using test tubes (p. 554) is used. ‘The pre-formed¢ acetone is obtained by aeration of the cold solution ; if the solution be warmed both the pre-formed acetone and that from aceto-acetic acid is obtained ; finally acetone is obtained from hydroxybutyric acid by oxidation with bi- chromate (p. 596). ‘The comparison is made with the precipitate formed by a standard acetone solution containing *5 mgm. 140 parts HNO,, 5 parts H,SO,, 55 parts H,O. 2 This may be standardised against mercuric nitrate. 3 J. Biol. Chem., 1913, 16, 289, 293 ; 1914, 18, 507. . 4 Tbid., 1914, 18, 263. 38
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