To the EDITOR.

SIR,-AS some photographers seem bent upon introducing a new term into the chemical dictionary--" albuminate of silver"--it behoves them to see they have good authority for so doing, lest we should some fine day derisively draw upon ourselves another new term-"photo chemists.'

The only experiment I have seen published for proving the existence of this chemical compound is that of adding a solution of albumen to a solution of oxide of silver, the resulting precipitate being dubbed albuminate of silver, without any after research to establish the fact.

Now, supposing albumen pur et simple does combine chemically with oxide of silver, what is the result of adding it to nitrate of silver ?

The albumen unites with the oxide, liberating nitric acid; but as nitric acid also precipitates albumen, another quasi chemical is formed, which I suppose, must be called nitrate of albumen - I should scarcely think the founders of the albuminous theory would call it albuminate of nitrogen Therefore, the film left on the sensitised plate would be albuminate of silver, the other albuminate compound. Now, if we admit the chemical combination with silver, why not also with the other metals, and thus introduce an extensive range of albuminates? ?

I make no attempt to disprove the chemical affinity. My only object is to protest against the acceptance of an ideal deduction drawn from a simple experiment of there being a new combination of silver, ignored by all the highest authorities on chemical science.

Amongst the great variety of substances that coagulate albumen [is?] tannin. Query-Would this be called tannate of albumen, or albuminate of tannin.-I am yours, &c.

Islington, May 3, 1859. THOS. A. BARBER

[Albuminate of silver is clearly a misnomer, as it indicates an ac[illegible?] oxide of albumen united to oxide of silver. It has, however, been clearly demonstrated by Mr. Hardwich that a compound of some kind, sensitive to the chemical rays of light, is formed by the union of white of egg and nitrate of silver: further, that a photograph on albumenised paper consists of metallic silver in combination with albumen, or, at any rate an organic substance; but what is the exact nature of these combinations has scarcely yet been ascertained. We think the term albumenide of silver would be less objectionable. ED.]