390 Scientific Notices — Chemistry. [May, 



nomenclature in its present state scarcely affords a concise, and, 

 at the same time, a definite appellation for this class of com- 

 pounds. The German chemists express them without difficulty, 

 and on precisely the same principles by which they express tne 

 compounds of metals with sulphur, &c. We have already no 

 hesitation in employing the terms seleniuret, arseniuret, &c. 

 Might we not extend the usage somewhat further, and designate 

 metallic alloys in general by the termination uret : thus, potas- 

 siuret, plumburet, stannuret. See. ? 



2. Conversion of Gallic Acid into Ubnin by Oxygen Gas. 



Accordino; to Dobereiner, when a solution of g-allic acid in 

 liquid ammonia is placed in contact with oxygen gas, it gra- 

 dually absorbs as much of the latter as is requisite to convert 

 the whole of its hydrogen into water. 100 parts of the acid 

 absorb 38*09 parts of oxygen. In the ordinary atmospheric 

 temperatures, the absorption is complete at the end of from 18 

 to 24 hours. While this change is going on, the solution 

 becomes intensely brown coloured and opaque, and on the addi- 

 tion of muriatic acid, it lets fall a a pale brown colouredjiocculent 

 substance, ivhich possesses all the characters of Ulmin. From 

 this experiment Dobereiner considers it probable that ulmin con- 

 sists of an atom of oxide of carbon (=12 carbon + 8 oxygen) 

 in combination with an atom of water (=1 hydrogen + 8 oxy- 

 gen) : it is certain, at least, that if the details of the experiment 

 be accurate, the constituents of the gallic acid (according to 

 Berzehus's analysis) taken in conjunction with the absorbed 

 oxygen, are resolvable into this simple ratio of atoms. 



Gallic acid prepared by Scheele's process, even after having 

 been crystallized from absolute alcohol, absorbs considerably 

 less oxygen than the sublimed acid, and it appears, therefore, 

 to be still contaminated with tannin, or with some other foreign 

 admixture. — (Pneumatische Chemie, Vierter Theil.) 



3. Formic Acid. — Formic Ether. 



Formic acid may be easily analyzed by mixing it either uncom- 

 bined, or in the state of a neutral salt, with from 6 to 10 times 

 its weight of concentrated sulphuric acid : it is instantly resolved 

 with effervescence into 24*30 parts of water, and 75*70 parts of 

 carbonic oxide gas. 



Hence it may be regarded as constituted of 1 volume of the 

 vapour of water + 2 volumes of carbonic oxide gas. This sup- 

 position is strengthened by the facility w ith which it is converted 

 into carbonic acid and water by the action of the oxides of silver 

 and of mercury. 



When formic ether stands in contact with water, it is gradually 

 decomposed into formic acid and alcohol ; during the decompo- 



