236 . dN PRtTSSIC ACfl5. 



or will ch remains in the casks. This proves, tst, that fer- 

 mentation cannot commence without the assistance of 0x1° 

 gen ; and 2dly, that, at equal deorees of acidity, the sul- 

 phurous acid prevents fermentation better than any other. 



Farther expe- jyTy labours at present are far from complete. 1 have in- 



nments . '. ipi-» 



iixiended, itituted many experiments, the results or which yet remain 



to be known, or which require to be revised ; and I resf^Tve 



them for a more extensive disquisition, that will embrace 



other objects. 1 confine myself therefore to this abstract. 



Action of ajjfj glmli conclude with observinoj, that very pure suaar, as 



sugar and r t 1 • in 



manna on ^v^" as manna, has the property 01 dissolving the yellovir 

 lead. oxide of lead, and of acting afterward on colours in the 



same manner as the alkalis. 



IV. 



Note on Prussic Acid: by Mr. Gay-Lussac*. 



Little informa- S^INCE the discovery of prussic acid by Scheele, and the 

 tiooof late labours of Messrs. Berthollet and Clouet, nothing very im* 



rcspcctinc . o •/ 



prussic acii, portant has been brought forward on the nature of this acid, 

 though both q^fjouffh the mobility of its elements has permitted it to be 

 decomposed ,,,-, , j. 



and cpmposed. decomposed, and it has even been composed by passing 



amraoniacal gas over redhot charcoal, it has not yet been 

 • obtained perfectly pure, so that we know.no;t under what 

 Its form when form it would preseht itself in tliis state. I have endea- 

 ^^'^' voured to solve thisquestion, and I shall prove in this note, 



that prussic acid is not permanently elastic ; that it forms a 

 liquid much more volatile than sulphuric ether, since it 

 boils at 26'5° [/Q'?" F-] ; and that, owing to this property, 

 at a temperature from 20° to 26^ [68® to 78-8° F.] it dilates 

 considerably the air or gasses with which it is mixed, com- 

 municates to them its properties, and tiien resembles a per- 

 manently elastic fluid. 

 Attempt to Desirous of ascertaining, for the purpose of a particular 



obtain it 3«. inquiry, whether prussic acid might be obtained in the 



* Ann. de Chim. vol. LXXVll, p. 128. Read to the Institute 

 Feb. I8il. 



gaseous 



