768 
MR. BRODIE ON THE CONDITION OF CERTAIN ELEMENTS 
In contact with strong hydrochloric acid hydrogen is evolved, and the protochloride 
of copper, CU2CI, formed. Both substances are decomposed, and Wurz satisfied 
himself, and gives the experiments, which show that the volume of the hydrogen 
evolved was the double of that due to the simple decomposition of the substance. I 
will add the remark which he makes on this experiment ; — “ On salt que I’acide 
chlorhydrique n’attaque le cuivre qu’avec une extreme difficult^, et la presence de 
I’hydrogene, loin de favoriser la reaction, devrait, d’apres les lois de I’affinite, y 
ajouter un nouvel obstacle. La decomposition de riiydrure de cuivre par I’acide 
chlorhydrique parait done s’etfectuer en vertu d’une action de contact*.” 
This fact, the conception of which offers these theoretical difficulties, becomes per- 
fectly intelligible, and indeed might have been predicted from the principles I have laid 
down. The decomposition is perfectly similar to that of the suboxide of copper under 
analogous circumstances, arises from the same cause, and may be expressed thus — 
+ — H — 
Cu2HHC1=Cu2C1-1-H2. 
This experiment enables us to see clearly the cause of a class of decompositions very 
analogous to it, and which have presented similar theoretical difficulties-f-. An alloy 
of platinum and silver will dissolve in nitric acid, which will not act upon the plati- 
num alone; acids will, in like manner, dissolve the alloy of copper and zinc:^:, which 
on the copper alone have no action. Now the hydruret of copper is itself, in its che- 
mical relations, an alloy, and the action of the acid on the alloy of copper and zinc is 
a fact very analogous to the action of the hydrochloric acid upon this body, and the 
explanation of this fact involves similar phenomena ; thus — ■ 
+ — + — + — 
H Cl Zn Cu Cl H = C 1 Zn+Cu Cl + H„ 
) 
the polar composition of the hydrogen being essential to. the comprehension of the 
experiment. A further confirmation of this view is found in the decomposition by 
water of the remarkable bodies discovered by Frankland§, to which he has given 
the names of zinc-methyl and zinc-ethyl. The theoretical analogy of these bodies to 
the hydrogen compounds of the metal is perfect, and with water they give a precisely 
similar reaction to that of the hydruret of copper with hydrochloric acid. Zinc-ethyl, 
for example, breaks up thus — 
_l_ — -I — 
Zn C4 H5H0 = C4 H5 Il-fZnO, 
k ; 
ill which decomposition the hydrogen and the hydrocarbon (which is the analogue of 
* Annales de Chimie, 3rd Series, vol. xi. 251. 
t These facts have been cited by Liebig with another view. Liebig’s Annalen, vol. xxx. p. 262. 
I Gmelin’s Handbuch, vol. iii. p. 448. § Journal of the Chemical Society, January 1850. 
