286 MM. Deville and Le Blanc on the Gaseous Emanations 



It will only be after the complete exposition of our investigations 

 that we shall be able to devote ourselves to the discussion of the 

 hypotheses suggested by the totality of the facts, and that we 

 shall show the relations of these singular strata with the principal 

 geological conditions of the country. 



To collect the gases, v\e have in general employed the same 

 means which have been described in our previous memoir upon 

 the volcanic emanations of Southern Italy*. Nevertheless the 

 circumstance of the evolution of gases under pressure at the sur- 

 face of the soil, and the facility with which the points of emanation 

 may be surrounded, have permitted us to fill tubes open at both 

 ends, which we then sealed with the blowpipe, after having cleared 

 them of air by the gaseous current itself; the latter had been 

 previously freed from aqueous vapour by its passage through a 

 WoolFs apparatus. The greater part of the water was deposited 

 by simple condensation in a bottle; the last traces of aqueous 

 vapour were retained by the passage of the gas thi'ough concen- 

 trated sulphuric acid. The violence of the current effected a 

 rapid displacement of the air in the vessels. 



We shall now pass in review the various localities in which we 

 have experimeutSd, and present a summary of the results of our 

 analytical investigations. 



Larderello, or Monte Cerboli. 



This is the first and the most considerable of the establish- 

 ments in which boracic acid is manufactured. The numerous 



the waters of hasins which have been for a certain time the recipients 

 of the currents of vapour, — waters which, when evaporated afterwards 

 by means of the heat communicated by the vapom's of the soil, furnish 

 boracic acid. 



It will be understood that, on condensing the aqueous vapour carried up 

 by the soffioni, the small quantity of boracic acid cannot be detected in it 

 by evaporating the liquid ; for this acid will be carried along by the aqueous 

 vapour in virtue of the same mechanism which brings it to the surface. 

 On the other hand, by receiving the vapours of the soffioni in cold water, 

 the latter becomes charged with a certain quantity of boracic acid in con- 

 sequence of their condensation : this quantity goes on increasing up to a 

 certain limit ; but it \vill be evident that, after a certain moment, there 

 will be a loss of boracic acid by its being carried away by the vajjovu-s, a 

 loss which prevents the water from becoming saturated with acid, even by 

 continuing the passage of the vapom-s into the water of the basins much 

 longer than is usually done. M. Schmidt had already announced that the 

 water of condensation of the soffioni contained boracic acid ; this fact ap- 

 ])ears to us to be placed beyond a doubt by our experiments. We have 

 condensed the vapom's in great quantity, not in water, but in a solution of 

 jjotash ; the latter was then carefully saturated with pure sulphuric acid, 

 evaporated to dryness, and treated with alcohol to separate the sulphates 

 from the slightly acid residue. The alcoholic solution, when evaporated, 

 furnished a residue exhibiting aU the characters of boracic acid. 



* Ann. de Chim, et de Phys. 3 ser. vol. lii. p. 5. 



