The course of carbolic acid poisoning is very rapid. In 35 cases collected by Falck, in which the period from the taking of the poison to the moment of death was accurately noted, the course was as follows:--12 patients died within the first hour, and in the second hour 3; so that within two hours 15 died. Between the third and the twelfth hour, 10 died; between the thirteenth and the twenty-fourth hour, 7 died; and between the twenty-fifth and the sixtieth hour, only 3 died. Therefore, slightly over 71 per cent. died within twelve hours, and 91·4 per cent. within the twenty-four hours. § 226. =Changes in the Urine.=--The urine of patients who have absorbed in any way carbolic acid is dark in colour, and may smell strongly of the acid. It is now established--chiefly by the experiments and observations of Baumann[205]--that carbolic acid, when introduced into the body, is mainly eliminated in the form of phenyl-sulphuric acid, C₆H₅HSO₄, or more strictly speaking as potassic phenyl-sulphate, C₆H₅KSO₄, a substance which is not precipitated by chloride of barium until it has been decomposed by boiling with a mineral acid. Cresol is similarly excreted as cresol-sulphuric acid, C₆H₄CH₃HSO₄, ortho-, meta-, or para-, according to the kind of cresol injected; a portion may also appear as hydro-tolu-chinone-sulphuric acid. Hence it is that, with doses of phenol or cresol continually increasing, the amount of sulphates naturally in the urine (as estimated by simply acidifying with hydrochloric acid, and precipitating in the cold with chloride of barium) continually decreases, and may at last vanish, for all the sulphuric acid present is united with the phenol. On the other hand, the precipitate obtained by prolonged boiling of the strongly acidified urine, after filtering off any BaSO₄ thrown down in the cold, is ever increasing. [205] _Pflüger’s Archiv_, 13, 1876, 289. Thus, a dog voided urine which contained in 100 c.c., ·262 grm. of precipitable sulphuric acid, and ·006 of organically-combined sulphuric acid; his back was now painted with carbolic acid, and the normal proportions were reversed, the precipitable sulphuric acid became ·004 grm., while the organically-combined was ·190 in 100 c.c. In addition to phenyl-sulphuric acid, it is now sufficiently established[206] that hydroquinone ( OH) (C₆H₄ ) ( OH) (paradihydroxyl phenol) and pyrocatechin ( OH) (C₆H₄ ) ( OH)