398 PHILOSOPHICAL TRANSACTIONS. [aNNO l/S/. 



united to more than its natural proportion of fixed air, as Mr. C. has showed that 

 this earth is actually united to more than double its natural proportion of fixed 

 air, and also that it is immediately precipitated, either by driving off the super- 

 fluous fixed air by heat, or absorbing it by the addition of a projjer quantity of 

 lime-water. 



Calcarious earths, in their natural state, i. e. saturated with fixed air, are totally 

 insoluble in water; but the same earths, entirely deprived of their fixed air, i. e. 

 converted into lime, are in some measure soluble in it; for lime-water is nothing 

 more than a solution of a small quantity of lime in water. It is very remarkable 

 therefore, that calcarious earths should also be rendered soluble in water, by 

 furnishing them with more than their natural proportion of fixed air, i. e. that 

 they should be rendered soluble, both by depriving them of their fixed air, and 

 by furnishing them with more than their natural quantity of it. Yet, strange 

 as this may appear, the following experiments, he thinks, show plainly that it is 

 the real case. • ," 



Exper. 5. — In order to see whether he could suspend a calcarious earth in 

 water, by furnishing it with more than its natural proportion of fixed air, Mr. C. 

 took 30 oz. of rain water, and divided it into 2 parts: into 1 part he put as 

 much spirit of salt as would dissolve dO^ grs. of calcarious earth, and as much 

 of a saturated solution of chalk, in spirit of salt, as contained 20 grs. of 

 calcarious earth: in the other part he put as much fixed alkali, as was equivalent 

 to 46-j«j- grs. of calcarious earth, i. e. which would saturate as much acid. This 

 alkali was known to contain as much fixed air as 3g grs. of calcarious earth. 

 The whole was then mixed together, and the bottle immediately stopped. The 

 alkali was before said to be equivalent to 46-pV grs. of calcarious earth, and was 

 therefore sufficient to saturate all the spirit of salt, and also to decompound as 

 much of the solution of chalk as contains \6^ grs. of earth. This mixture 

 therefore, supposing he made no mistake in his calculation, contained l6i grs. 

 of unneutralized earth, with as much fixed air as is contained in SQ grs. of 

 calcarious earth; which is the quantity which was found to be in the same 

 quantity of Rathbone-place water. The mixture became turbid on first mixing, 

 but the earth was quickly re-dissolved on shaking, so that the liquor became 

 almost transparent. After standing some time, a slight sediment fell to the 

 bottom, leaving the liquor perfectly transparent. The mixture was kept 3 or 4 

 days stopped up, during which time it remained perfectly clear, without depositing 

 any more sediment. The clear liquor was then poured off, from the sediment, 

 and boiled for a few minutes, in a Florence flask ; it became turbid before it began 

 to boil, and discharged a good deal of air; some earth was precipitated during 

 boiling, which being dried weighed 13 grs. This shows that there was really, at 

 least, 13 grs. of earth suspended in this mixture, without being neutralized by any 



