646 Proceedings of the Royal Society 
of the sulphur by hydrogen will generate very different bodies. 
Theory enables us to predict that, in the case of bodies having the 
constitutional formulae of No. (5), we ought to obtain alanine. 
In that of (3) (jS) alanine, and in that of (4) amido-lactic acid 
(serine), and in that of (2) amido-glycerine ; whereas it is diffi- 
cult to imagine the sulphur in (1) being replaced. A success- 
ful experiment in this direction ought to restrict the selection to 
two possible constitutional formulas in the worst case, and syn- 
thetical processes might then be attempted. It was formerly 
observed that nascent hydrogen generated in an acid solution, 
readily liberated sulphuretted hydrogen, and might be used as a 
test for this substance. The action goes on, however, very slowly, 
and it was found extremely difficult to get anything like the theo- 
retical quantity of sulphur evolved. With this experience, sodium 
amalgam suggested itself as being more powerful, and equally 
likely to act. When cystine is dissolved in caustic soda, and 
sodium amalgam added, in a few minutes it is easy to detect the 
presence of a sulphide by the nitro-prusside test. The action was 
allowed to proceed for several days, being occasionally rendered 
acid by the addition of hydrochloric imid, and the amalgam renewed. 
Ultimately the alkaline solution, after being neutralised with 
hydrochloric acid, was evaporated and treated with boiling alcohol 
to separate the chloride of sodium, and to dissolve any hydro- 
chlorate of alanine that might be formed. After the filtrate was 
evaporated, the residue still contained sulphur, from the presence 
of hydrochlorate of cystine. This was separated by treating with 
water, and the filtrate was boiled with oxide of lead, treated after- 
wards with sulphuretted hydrogen to precipitate the dissolved lead, 
and evaporated. The residue was then heated to 200 0. in a tube, 
with the object of subliming the alanine. No crystalline subli- 
mate was observed ; it is probable, therefore, that substances of 
the constitutional formulae of 5 do not express the constitution 
of normal cystine. This result is subject to a certain amount 
of reservation, from the difficulty of separating a small quantity 
of substance from a very large amount of secondary material 
accumulated in the course of the experiment. The battery is far 
better adapted to give a supply of nascent hydrogen in this case; 
and an experiment male in this way looks promising, if sufficient 
material was to be had. 
