Mr. Connell on the 'Nature of Lam pic Acid. 515 



With oxide of silver and lampic acid there was, when hea* 

 was applied, the like effervescence and evolution of carbonic 

 acid, which made lime-water muddy ; and after the liquid had 

 been evaporated away on the sand-bath, the residue was me- 

 tallic silver. 



In these circumstances we cannot hesitate to say that lampic 

 acid reduces the salts and oxides of mercury and silver with 

 effervescence and evolution of carbonic acid *. 



This quality, it is unnecessary to state, is a property of 

 formic acid. It was also formerly shown that perfectly well 

 characterised formates of magnesia and of lead may be ob- 



* Although it is quite true that Professor Daniell does not state on all 

 occasions that lampic acid reduces these salts with effervescence, yet it is 

 equally certain that he nowhere says that it reduces them without effer- 

 vescence; and M. Liebig appears to have overlooked one or two passages 

 which seem to prove sufficiently that Mr. Daniell was perfectly aware that 

 lampic acid reduces these salts with effervescence and evolution of carbonic 

 acid. After stating (Journ. lnstit.,\o\. vi. p. 323) that lampate of mercury 

 when heated was reduced with "violent effervescence," he adds, that wishing 

 to know " the nature of this decomposition of the metallic oxides,'* he 

 heated black oxide of manganese with lampic acid, and found that carbonic 

 acid was given off, which precipitated lime water ; an experiment which 

 I have made with the like result. 



A circumstance was observed in the course of my experiments which is 

 connected with the existence of substances not of an acid nature in the 

 liquid, and which J shall merely notice for the use of any one who may wish 

 to make these substances the subject of a separate study. When pure lampic 

 acid is heated to from 150° to 160° Fahr. an evolution of permanently 

 elastic fluid commences, and if the heat is gradually increased as occasion 

 requires, a quantity of permanently elastic fluid is evolved, amounting to nine 

 or ten times the bulk of the liquid employed. When the gas so evolved 

 is collected over mercury and washed either with pure water or lime water, 

 about one sixth of it is absorbed, and the lime water does not become 

 muddy. The part absorbed appears merely to be vapour either of the 

 acid or of some aethereal product. The residual gas was found to be in- 

 flammable, and when analysed in the voltaic eudiometer proved to be 

 hydrogen nearly quite pure. Conformably with this result it was found 

 that when the gas evolved from a heated mixture of lampic acid and the 

 salts or oxides of mercury or silver was collected over mercury, about one 

 third only of its bulk, and sometimes somewhat less, was absorbed by lime- 

 water with precipitation of carbonate of lime; and the residue on analysis 

 proved to be hydrogen. On the other hand, if the acid was first heated 

 till permanently elastic fluid no longer was evolved, and then mixed with 

 protonitrate of mercury and again heated, the salt was reduced with effer- 

 vescence and evolution of carbonic acid without any mixture of inflam- 

 mable gas. In like manner if the acid was saturated with soda and eva- 

 porated to dryness, and the salt thus got was redissolved in water, and 

 mixed with protonitrate of mercury and heated, the salt of mercury was 

 reduced with evolution of carbonic acid without inflammable gas. The 

 origin of this hydrogen was not further investigated, because its presence 

 was evidently altogether unconnected with the properties of the acid con- 

 tained in the liquid ; these properties being the same whether the liquid 

 had been previously heated or not. 



3 U 2 



