VOL. LVn.] PHILOSOPHICAL TRANSACTIONS. SQQ 



acid; the suspicion of which could be owing only to its being united to more than 

 its natural proportion of fixed air. But as a further proof of this, Mr. C. made the 

 following experiment. 



Exper. 6. — He took the same quantities of rain water, solution of chalk, 

 spirit of salt, and fixed alkali, as in the last experiment, but mixed them in a 

 different order. The fixed alkali was first dropped into the spirit of salt, and 

 when the effervescence was over, was diluted with -^ the rain water. The solution 

 of chalk was then diluted with the remainder of the rain water, the whole mixed 

 together, and the bottle immediately stopped, and shaken vehemently. A preci- 

 pitate was immediately formed on mixing, which could not be re-dissolved on 

 shaking. 



It must be observed, that in the first of the 2 foregoing experiments, all the 

 fixed air contained in the alkali was retained in the mixture, none being lost by 

 effervescence; whereas, in the last experiment, the greatest part of the fixed air 

 was dissipated in the effervescence; no more being retained than what was con- 

 tained in that portion of the fixed alkali, which was not neutralized by the acid; 

 and consequently the unneutralized earth, in the mixture, contained not much 

 more fixed air than what was sufficient to saturate it. As the latter of these 

 mixtures differed no otherwise from the former, than that it contained less fixed 

 air, the suspension of the earth in the former must necessarily be owing to the 

 fixed air. 



In the 2 foregoing experiments the water contained, besides the unneutralized 

 earth and fixed air, some sal sylvii, and a little solution of chalk in the marine 

 acid; which, it may be supposed, contributed to the suspension of the earth: but 

 the following experiment shows that a calcarious earth may be suspended in 

 water, without the addition of any other substance than fixed air. 



Exper. 7. — A bottle full of rain water was inverted into a vessel of rain water, 

 and some fixed air forced up into the bottle, at different times, till the water had 

 absorbed as much fixed air as it would readily do; 11 oz. of this water were 

 mixed with 64- of lime water. The mixture became turbid on first mixing, but 

 quickly recovered its transparency, on shaking, and has remained so for upwards 

 of a year. This mixture contains 7 grs. of calcarious earth ; and, from a sub- 

 sequent experiment, he guessed it to contain as much fixed air as there is in 14 

 grs. of calcarious earth. 



Exper. 8. — Lest it should be supposed, that the reason why the earth was 

 not precipitated in the foregoing experiment, was, that it was not furnished with 

 a sufficient quantity of fixed air, the following mixture was made, which contains 

 the same proportion of earth as the former, but a less proportion of fixed air: 

 4-f^ oz. of the above mentioned water, containing fixed air, were diluted with 6-i- 



