178 Report upon a Memoir on the Nitrons FAhef,- 



and a specific smell, give to ethers a decided character, 

 which does not admit of their being confounded with other 

 substances. We know but imperfectly, however, the differ- 

 ences which distinguish them from each other; aiMl in par- 

 ticular, we have but an imperfect theory upon their produc- 

 tion. Messrs. Fourcroy and Vauquelin have indeed thrown 

 a great deal of light upon the production of the sulphuric 

 ether ; but their explanation cannot be extended to that of 

 some other ethers. It was therefore important to resume 

 the subject, in order to treat it in a general manner. This is 

 whatM. Thenard undertook; — In the first memoir present- 

 ed to the Institute, he treats of the nitric ether. He will 

 afterwards proceed to the others ; and will examine why 

 some acids have the property of producing ethers, while 

 others are deprived of it. 



M. Thenard first brings under review the processes re- 

 commended by chemists for producing the nitric ether. 

 These are very discordant, and only have for their object the 

 etherized liquof, which we may obtain without any analysis 

 ©f the gaseous products, nor any consideration of the cir- 

 cumstances of the operation, unless we except the Dutch 

 chemists, in a memoir which has particularly occupied M* 

 Thenard*s attention, at the end of his own, 



M. Thenard began by distilling a mixture of equal weight 

 of alcohol and nitric acid, both being of a determinate con- 

 centration, in an apparatus proper for separating the liquid 

 products from the gaseous ; a slight heat is sufficient, and 

 even the action becomes so brisk that it is soon necessary 

 to check it. He afterwards examined the residue of the 

 retort, the liquid produce, and the gases. The residue wa;? 

 composed of nitrous acid, acetic acid, alcohol, water, and a 

 little of a matter the nature of which is not determined, 

 but which chars easily. The proportions of these sub- 

 stances are established by ingenious and precise means. But 

 we are obliged to pass over the details necessary for a cfear 

 idea of the numerous operations M. Thenard's experiments 

 require ; — if we push the distillation to dryness, the viscous 

 residue contains oxalic acid, and probably malic acid. 



The liquor distilled, which has been regarded in laboratories 



as 



