WATER IN MURIATIC ACID OAS. 



265 



salt absorbs no water from the air, and that it affords water Muriate of 

 when heated, though the air has been excluded. The same ® oJ . absor b 

 results were obtained by Drs. Bostock and Traill. It remained, wat*>r from 

 therefore, for Sir Humphry either to shew that they were the air * 

 not correct, or to establish, by farther evidence, his former 

 statement. With this view the experiment, above alluded to, 

 has been performed. About go cubic inches of muriatic 

 acid gas were combined with the requisite quantity of ammo- 

 niacal gas, in an exhausted retort of the capacity of 26 cubic 

 inches, and the sale formed having been heated in the same re- 

 tort, closed at its extremity by a stop-cock, water was obtained 

 from it in small quantity, " a dew just perceptible lining the 

 cold neck." On this experiment I have how to offer a few ob- 

 servations, and I have to state the result of another since per- 

 formed. 



When the experiment was made, I was informed by Df. The retort in 



Hope of the result, and of the manner in which it had been Sir H.Davyi 



r t experiment 



executed. I stated to him in what respect it appeared to me was too large, 



objectionable, independent of the unfavourable circumstances 

 inseparable from the mode of heating the salt in a close vessel ; 

 the large size of the retort rendering it difficult to apply the 

 heat equally, so as to expel the water from one part without 

 its condensing in another, allowing, too, a larger portion of any ' 

 vapour disengaged to remain in the elastic form while the heat 

 was kept high, and equally permitting its condensation wheri 

 the heat diminished over an extensive surface, encrusted with a 

 substance by which it would be absorbed, the unequal applica- 

 tion of the heat producing a similar volatilization from one 

 part, and condensation in another, the confinement of the And the coto* 

 heated elastic fluid operating by its pressure in resisting the sepa- y^™^*^. 

 ration of the water from the salt, and by its temperature cOUn- paration and 

 teracting the local condensation of the portion evaporated, and condensation 

 lastly, the encrustation of salt which had been allowed to remain 

 at the curvature and upper part of the neck of the retort, 

 where, in such an experiment, the condens tion of moisture 

 chiefly takes place, were all unfavourable to the result. If the 

 experiment had been one in which a considerable quantity of 

 wattr was to be looked for, these circumstances might have 

 been of less importance. But this not being the case, it was 

 more necessary to attend to their influence, and every arrange- 

 Vet. XXXIV.— No. 159. T ment 



