As modified in 1905 from an earlier description, which had been found unsatisfactory by various observers,2 this process is as follows.3

The spirit, after distillation to free it from any colouring or extractive matter, is diluted with water until it contains not more than 20 per cent. of alcohol by volume. Fifty c.c. of this diluted spirit are taken, and extracted with four successive quantities of carbon tetrachloride, using 50 c.c. of the latter each time and shaking vigorously for a few seconds. The united carbon tetrachloride extracts are washed twice with about 20 c.c. of water, and then treated in a stoppered flask with 2 grams of potassium bi-sulphate and 1 gram of sodium nitrite, powdered together. After shaking for a few minutes, the mixture is transferred to a separating funnel, the tetrachloride drawn off, and the residue extracted twice with a little more carbon tetrachloride. The whole of the extracts are now shaken with about 20 c.c. of a saturated solution of sodium bicarbonate to remove excess of nitrous acid; separated; and then carefully mixed with about 75 c.c. of strong sulphuric acid previously placed in a separating funnel. After being well shaken, the mixture is run on to about 150 grams of crushed ice and the resulting solution titrated with standard permanganate solution (1 in 1,000). In order to obtain a sharp end-point, an excess of the permanganate, about 20 per cent. more than is used up, should be added, and the excess titrated back with standard solution of ferrous-ammonium sulphate. Each c.c. of the permanganate solution used up = 000278 gram of amyl alcohol.

1 Schidrowitz and Kaye, Analyst, 1906, 31, 183.

2 Schidrowitz, ibid., 1905, 30, 192; Bedford and Jenks, J. Soc. Chem, Ind., 1907, 26, 123.

3 Zeitsch. Nahr. Genussm., 1905, 10, 143-152.

Bedford and Jenks1 have modified this process, first, by improved extraction and washing, and secondly by estimating the nitrites icdometrically. They proceed as follows.

(A)

To 30 c.c. of the spirit, diluted to 20 per cent. strength and contained in a separator, 25 grams of dry granular calcium chloride are added, the separator being cooled under the tap meanwhile.

(B)

The liquid is then shaken for seven minutes with two successive quantities of 50 c.c. of carbon tetrachloride.

(C)

The resulting 100 c.c. of extract is washed with two successive quantities, 30 c.c. each, of saturated calcium chloride solution (D = 14).

(D)

The washed carbon tetrachloride solution of higher alcohols is then treated with 2 grams of potassium bisulphate and 1 gram of sodium nitrite (powdered together) to convert the alcohols into the nitrites. The vessel used should be dry, not too large, and kept stoppered. A small tapped and stoppered separating funnel of about 170 c.c. capacity serves the purpose well.

(E)

The nitrites, after washing with solution of sodium bicarbonate and separation of the latter, as in the original process, are determined by Dunstan and Dymond's method,2 with potassium iodide in acid solution in absence of free oxygen, the iodine thus liberated being titrated with thiosulphate solution. The reaction is based upon the following equation: ently hung on a cotton-wrapped ring on a retort stand. The tap and its socket must be perfectly clean and dry before use, and should be freely covered with vaseline.

2HI + 2HNO2 = 2H1O + 2NO + I2.

Details of manipulation are given in the original paper of Dunstan and Dymond, and also in Sutton's " Volumetric Analysis " (p. 286 of the 1911 edition), but a modification of the apparatus is preferred by Bedford and Jenks, on account of the action of carbon tetrachloride on the rubber joint.

These authors use an ordinary pear-shaped separator funnel of about 350 c.c. capacity and 3 1/2 inches diameter, provided with a well-ground stopper and tap. The stem is about 2 in. long, is cut off obliquely, and passes through a rubber stopper to a round-bottomed flask of about 250 c.c. capacity. The whole is conveni-

1 J. Soc. Chem. hid., 1907, 26, 123. 2 Pharm. J., 18S9 , [iii], 19, 741.

Five c.c. of a 10 per cent. solution of potassium iodide, 5 c.c. of a 10 per cent. solution of sulphuric acid, and 40 c.c. of water are introduced into the flask, and the tap of the funnel being open, the mixture is boiled so as completely to expel the air from the flask. When the volume of the liquid has been reduced to about 10 c.c., the flame is removed with one hand, the tap is simultaneously closed with the other, and then screwed firmly into position with both hands. If the tap has been properly dried and greased at the start it will remain air-tight, and will move freely when the apparatus is cold, though it may appear to be jammed whilst cooling is taking place.

The carbon tetrachloride solution of the nitrites is passed into the cooled flask through the separator, care being taken that no air is admitted, and then 20 c.c. of alcohol (ordinary rectified spirit) are also run in. The nitrites are quantitatively decomposed, usually after vigorous shaking for a few minutes, though it is desirable to allow the flask to stand for about an hour before actual titration, and to keep it under observation for some hours longer.

The liberated iodine is titrated with decinormal thiosulphate solution, which is run from a burette into the separator, and gradually drawn into the flask by means of the tap. As soon as the iodine is decolorised any excess of thiosulphate remaining in the separator is returned to the burette; or more accurately, it may be titrated separately with standard iodine solution to ascertain its amount. From the volume of thiosulphate used up, the quantity of nitrous acid is calculated from the equation given, and thence the equivalent amount of amyl or other nitrite is obtained.

This method gave the authors very good results when tested upon known quantities of the individual higher alcohols - amyl, n-butyl, isobutyl, and n-propyl. The quantities found were generally within about 5 per cent. of the amounts added. With isopropyl alcohol, however, only about 70 per cent. of the added quantity was shown in the results. When samples of commercial spirits were examined the results obtained, as would be expected, were generally higher than those given by the Allen-Marquardt process, and sometimes considerably higher. The authors look upon the difference as a measure of the "intermediate" higher alcohols.