442 Manufacture of Platinum. — Humis Test for Arsenic. 



that it is a kind of naphtha, containing 89 per cent, carbon, 

 and explains his finding too little by the circumstance that the 

 fluid contains phosphuretted hydrogen, from which it is with 

 difficulty freed. {Annales de Chim. et de Phi/s. Ixxv.) 



LXXI. On the Mamfacture of Platinum. By a corre- 

 spondent. 



To the Editors of the Philosophical Magazi7ie and Journal. 

 Gentlemen, 



WILL you allow me, through your pages, to suggest to 

 chemists that the price of that necessary article, pla- 

 tinum, might be reduced by means of the electrotype process? 

 I believe that the high price of this metal is in some measure 

 due to the labour required to reduce it into a malleable state 

 by the method of Wollaston. This portion of the expense 

 might, I think, be reduced to a very small part of the whole, 

 if the metal were at once reduced from its solution by the slow 

 action of electricity, as this mode involves no labour, while 

 the necessary apparatus is cheap. Might not the same method 

 be applied to reduce nickel to a malleable state? This being 

 a cheap metal, not liable to rust, it might perhaps be advan- 

 tageously used for some purposes for which platinum is too 

 expensive. 



I am, Gentlemen, your obedient servant, 



C. 



LXXIL On testing for Arsenic and Antimony by Hume's 

 Process. By J. Marsh, Esq. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



IF you should think the following communication of suffi- 

 cient importance, I beg you will give it a place in your 

 valuable Journal. 



In testing for arsenic I have found, by repeated experiments, 

 that Hume's test (the ammonia-nitrate of silver) is extremely 

 useful as a discriminative test for arsenic or antimony. The 

 way that I use it is simply as follows: — After the matter to 

 be tested has been acted on in my apparatus, a piece of com- 

 mon window-glass, (which I prefer, as it can be obtained with 

 ease,) porcelain or mica, is to have one of its surfaces moist- 

 ened with Hume's test; it is then to be held horizontally, with 

 its moistened side downwards, directly over the ignited jet of 

 gas, about half an inch from the tip of the flame. If arsenic 

 be present, the well-known characteristic lemon-yellow colour 



