950 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



feces, as sulphuretted hydrogen in the intestinal gas, as sulphate and other 

 unknown compounds in the urine. 



Detection. If a sulphur compound be fused with sodium carbonate on charcoal, the 

 sulphur will be reduced to sodium sulphide. The melted mass if placed with a drop of 

 water on a silver coin leaves a black spot of silver sulphide. 



Sulphuretted Hydrogen, H 2 S. This gas is found in the intestines, and 

 pathologically in the urine. 



Preparation. (1) Action of hydrochloric or sulphuric acid on ferrous 

 sulphide, 



This same reaction takes place by treating feces (which contain FeSj with acid. 



(2) From the putrefaction of proteids, and by boiling proteid with mineral 

 acid. 



Properties. Sulphuretted hydrogen unites readily with the alkalies and 

 with iron salts, forming sulphide ; hence little H 2 S is found in the intestinal 

 tract. It is a strong poison when respired. It has been shown in frogs to 

 enter into combination with oxy haemoglobin to form sulph-hsemoglobin, 

 and likewise rapidly kills the nerves. 1 Sulphuretted hydrogen diluted 

 with hydrogen and introduced into the rectum of a dog produces symptoms 

 of poisoning in one to two minutes (Planer). It has an offensive odor similar 

 to foul eggs. 



Detection. If a piece of filter-paper soaked in acetate of lead be brought in contact 

 with H 2 S, it turns black, owing to the formation of sulphide of lead (PbS). Soluble sul- 

 phides in alkaline solution give with sodium nitro-prussiate, Na 2 Fe(CN) 5 NO -f 2H 2 0, an 

 intense violet color, given also by acetone and aceto-acetic acid. 



Sulphurous Acid, H 2 S0 3 . This acid has been found in the urine of cats and dogs, 

 and has been detected by Striimpell in human urine in a case of typhoid fever. 



Sulphuric Acid, H 2 SO 4 . This acid is found in the urine in combination 

 with alkali (preformed sulphate), and with indol, skatol, cresol, and phenol 

 (ethereal sulphates). It is found in the saliva of various gastropods. 



Preparation. (1) By oxidation of sulphur with nitric acid, 



S + 2HN0 3 = H 2 SO 4 + 2NO. 



(2) By oxidation of sulphur-containing proteid. 



Properties. Sulphuric acid is a very powerful acid. It is produced in the 

 body by the burning of the proteids (which contain 0.5 to 1.5 per cent. S), 

 80 per cent, or more being oxidized to acid, while the remainder appears in the 

 urine in the unoxidized condition termed neutral sulphur. When proteid, fat, 

 and starch free from ash is fed to dogs, they "live only half as long as they 

 would were they starving, 2 for, according to Bunge, 3 the sulphuric acid formed 

 abstracts necessary salts from the tissue. (For further discussion of this see 

 pp. 956 and 969). 



Detection. if 100 cubic centimeters of urine be treated with 5 cubic centimeters of 



1 Harnack : Archivfiir experimentelle Pathologic und Pharmakologie, 1894, Bd. 34, p. 156. 



2 J. Foster: Zeitschrift filr Biologic, 1873, Bd. 9, p. 297. 



3 Physiologische Chemie, 2d ed., 1889, p. 104. 



