[189] Lancet, 1871.
§ 206. Excretion of Chloral.—Chloral hydrate is separated in the urine partly as urochloral acid (C8H11Cl3O7). Butylchloral is separated as butyl urochloral acid (C10H15Cl2O7). Urochloral acid is crystalline, soluble in water, in alcohol, and in ether, reduces copper from Fehling’s solution, and rotates a ray of polarised light to the left. Urochloral acid, on boiling with either dilute sulphuric or hydrochloric acid, splits up into trichlorethyl alcohol and glycuronic acid—
C8H11Cl3O7 + H2O = C2H3Cl3O + C6H10O7.
Trichloralcohol is an oily fluid (boiling-point 150°-152°); it yields by oxidation trichloracetic acid.
Urobutyl chloral acid gives on treatment with mineral acids trichlorbutyl alcohol and glycuronic acid.
To separate urochloral acid from the urine the following process has been found successful:—
The urine is evaporated to a syrup at the heat of the water-bath, and then strongly acidulated with sulphuric acid and repeatedly shaken out in a separating tube with a mixture of 3 vols. of ether and 1 vol. of alcohol. The ether-alcohol is separated and distilled off, the acid residue is neutralised with KHO, or potassic carbonate, and evaporated; the dry mass is then taken up with 90 per cent. alcohol, the filtrate precipitated with ether, and the precipitate washed with ether and absolute alcohol.
Next the precipitate is boiled with absolute alcohol and filtered hot. On cooling, the potassium salt of urochloral acid separates out in tufts of silky needles. The crystals are dried over sulphuric acid and again washed several times with absolute alcohol and ether to remove impurities.