of Edinburgh, Session 1869-70. 203 
cium. It is therefore evident that when an ammoniacal solution of 
cystine is heated with ammoniacal solution of oxide of silver, the 
sulphur is separated entirely as sulphide of silver, none being 
oxidised ; it is also obvious that no oxalic acid is formed. 
Action of Caustic Soda and Caustic Baryta on Cystine. 
Cystine, when treated with pure solution of pure NaHO, and 
evaporated in a silver basin, gives a reddish fluid ; sulphide of 
sodium is then produced, blackening the basin, and ammonia is 
copiously evolved. On treating the residue with water, neither 
sulphuric nor oxalic acids can be detected. The liquid contains, 
however, a large quantity of sulphide of sodium with a mere trace 
of sulphite. 
Cystine, when heated to 150° C. with solution of caustic baryta in 
sealed tubes, gave off ammonia, a large quantity of sulphide of 
barium, a smaller quantity of sulphite of barium, and a trace of 
hyposulphite being formed. No trace of sulphocyanide could be 
detected. 
Action of Alcoholic Solution of Potash on Cystine. 
Cystine was heated for several hours in a sealed tube at 130° C 
with an alcoholic solution of potash. At the conclusion of the 
experiment a small quantity of dark sticky matter was found 
adhering to the tube, which contained a yellowish fluid. The latter 
smelt strongly of ammonia, which was separated by distillation. 
The residue was acidified with dilute sulphuric acid, and shaken 
up with ether. Ether left a yellow non-crystalline substance, 
possessed of an indefinite but disagreeable odour. This substance 
had a strong acid reaction, and was found to contain no sulphur. 
Action of Nascent Hydrogen on Cystine. 
When cystine is added to a mixture of tin or zinc and dilute 
hydrochloric acid, large quantities of sulphurated hydrogen are 
given off ; the evolution of gas gradually slackens, till even after 
the action has gone on for several days, traces of sulphuretted 
hydrogen continue to be given off. When treated in the same 
manner taurine does not evolve H^S. 
It is to be noted that this evolution of H,S, when cystine is 
