1S13.] On a new Variety of Ulmin. 13 



aspect of silica, but were too minute to be subjected to a che- 

 mical examination. The addition of ammonia to the nitric acid 

 solution occasions the separation of a few flocks, which redissolve 

 by agitation. Carbonate of potash occasions a more copious 

 precipitate. Hence it would appear that the ash consists of 

 carbonate of lime, with some traces of magnesia and silica. 



This variety of ulmin resembles the bitter principle from coffee 

 described by Chenevix, and the tannin of Kino, in striking a 

 green colour with sulphate of iron. Its effect upon sulphate of 

 zinc I consider as its most remarkable property. Zinc is usually 

 precipitated of a white colour from its solutions ; but the ulmin 

 of the oak throws it down almost black. 



The appearance of the ulmin of the oak, its taste, and the tree 

 from which it was obtained, led me to expect that it would 

 contain tannin ; but if not forming a precipitate with gelatine be 

 characteristic of the absence of that principle, as we consider it 

 at present, we must conclude that the ulmin of the oak contains 

 no tannin whatever. 



Mr. Sowerby likewise collected ulmin from the hornbeam ; 

 but as he unfortunately mixed it with ulmin from the elm, it 

 was not possible to determine its peculiar characters. 1 mention 

 the circumstance to induce such of my readers as are interested 

 in the progress of vegetable chemistry, and have an opportunity 

 of examining the trunks of trees, to look for exudations from 

 them, that we may have information as speedily as possible of 

 the various trees that yield this hitherto neglected vegetable 

 principle. 



Article V. 



On Sir H. Davy's Theory of Chlorine, and its Compounds.* By 

 Mr. William Henderson, Member of the Royal Medical 

 Society of Edinburgh. 



TbB reasons which may be alleged in proof of the simple 

 nature of oxymuriatic gas seem easily reducible to four heads, 

 viz. : — 



I. It is converted into muriatic acid by union with hvdrogen; 

 and this change is unaccompanied by the evolution of any 

 aqu< ".is vapour. 



II. The products of its action on combustibles, and on metals, 

 differ essentially from those which ...i-.c bum the action of oxygen 

 on ihe same bodies. 



Thii enaj was honoured w i tii the prize medal of the Medical Society of 

 rdiuburgli for 1*12. 



