WATER IN MURIATIC ACID GAS. 267 



tities of gases had been employed as in that experiment, and I 

 need scarcely say, that every precaution had been taken to 

 exclude every source of fallacy. Some of the salt having 

 reached near to that place of the tube where the dew was con- 

 densedj part of the moisture seemed to have been resumed by 

 it during the cooling of the apparatus, and prevented Dr. Hope 

 from ascertaining with precision the quantity of the fluid. To 

 obtain an estimate of it, he next day put a little water into ano- 

 ther flask having a similar tube, previously weighed, fitted to 

 it by grinding, and applied heat to the flask till the inside of a 

 portion of the tube was covered with dew, and a drop of 

 water collected in the bottom, as in the preceding experiment. 

 The quantity of humidity, thus condensed, weighed one grain, 

 and in appearance so far exceeded that observed in the tube in the 

 experiment of the preceding day, as to lead tothe.conclusion, that 

 thelatter could not be estimated at more than two-thirds of a grain. 



Such is the result of these experiments intended to be deci- ^^^in-^ 8 

 siveof the question with regard to the state of the fact, whe- edbySirH.D. 



ther, when this salt is heated in close vessels, any water is ob- f" d , estJ V 

 i <• ■»*■ ^ <-<* \ . i bhshes the 



tamed from it or not. Messrs. Davys affirmed, in the most author's state- 

 explicit terms, that there is none ; Sir H. Davy " did not ob- ments, &c. 

 serve the slightest traces of moisture in making the experiment 

 on a larger scale in exhausted vessels." And Mr. J. Davy 

 found, that " no water was produced — not even the slightest 

 trace appeared." I affirmed, that though this mode of con- 

 ducting the experiment is unfavourable to the result, and is 

 not at all calculated to afford information with regard to the 

 real quantity which the salt yields, still a sensible portion of 

 water is obtained. It is now established, that my statement is 

 correct, that of my opponents the reverse. In the experiment, 

 as performed by Sir Humphry himself, a sensible portion of 

 water appeared, and when the obvious sources of fallacy at- 

 tending that experiment have been avoided, a larger quantity 

 has been obtained. 



To obviate the conclusion which might be drawn from this Remarks. The 

 result, Mr. J. Daw endeavours to show, that the quantity ob-"w p fv U r m *" 

 tained in his brother's experiment might be derived from extra- riment did not 



neous sources, from vapour in the gases, or moisture from the comt fx0m ex " 

 ' r & * . traneoua 



mercury. This it is scarcely necessary to discuss. Dr. sources. 

 Henry, he remarks, found that ammonia obstinately retains 

 aqueous vapour, yet Dr. Henry ■ states, that ammonia may be 



T2 so 



