236 Intelligence and Miscellaneous Articles. 



cumstances, except by the previous formation of hydrate of barytas 

 at the expense of a part of the water feebly retained by the sul- 

 phuric acid ; but the facts stated render this opinion inadmissible. 

 When employing acid of r848 density, the heat, as well as the 

 addition of a little water, occasions the reaction, and in the latter 

 case, the presence of the water unquestionably does not intervene, 

 except by the extrication of the requisite heat. This extrication 

 may be owing to different causes ; in the experiment C, it may be 

 attributed to the combination of a part of the water of the weak 

 acid with barytes, or the formation of hydrate of barytes ; and in 

 the experiment D, it is hydrate of barytes ready formed, which, be- 

 ing more favourable to combination, gives immediate rise to the 

 production of sulphate of barytes by its contact with sulphuric acid 

 of density 1-848. 



The explanations given by M. Braconnot of the non- action, under 

 certain circumstances, of the acids upon metals, their bases or car- 

 bonates, are not, in the opinion of M. Lassaigne, applicable to the 

 results of the experiments related ; they are equally unsatisfactory 

 in explaining the phasnomena observed by Proust, and which relate 

 to the action of nitric acid upon tin, — an action which gives rise to 

 the production of a compound which is insoluble (stannic acid), even 

 when the acid is in the state most favourable for energetic action. He 

 is also of opinion that in all the reactions described by MM. Proust, 

 Pelouze, and Braconnot, the great stability of the compounds of 

 acids and water, when they exist in the proportions stated with re- 

 spect to the weights of their atoms, exerts great influence ; and 

 that the mixture of alcohol and aether with the acids results, not 

 only from giving a liquid which is not susceptible of dissolving the 

 product which may arise from the reaction of these acids on the bases 

 or the carbonates, but from preventing all action from occurring by 

 taking from the acids the portions of water which are not retained 

 by stability of combination. The experiment E. gives support to 

 this opinion. 



In the contact of nitric acids with the metals, the presence of a 

 little uncombined water also undoubtedly intervenes to facilitate the 

 reaction. Ammonia, the formation of which occurs with iron, zinc, 

 and cadmium, as is the case with tin, favours this opinion ; but this 

 influence cannot be readily admitted with respect to lead, copper, 

 and sUver. 



In the course of these experiments, M. Lassaigne found that the 

 action of nitric acid upon the metals is always accompanied with 

 the formation of more or less ammonia, according as the metals de- 

 compose water more or less readily. The metals which do not de- 

 compose water yield no traces of ammonia. 



In operating upon potassium and sodium, nevertheless, he ob- 

 tained no traces of nitrate of ammonia, which he attributes to the 

 high temperature produced, and at which the nitrate of ammonia 

 cannot exist : these experiments with the metals of the alkaline ox- 

 ides are not free from danger, on account of the violent explosion 

 which takes place at the moment of contact between them and the 

 nitric acid. — Ann. de Chimie, Ixyii. 209. 



