VOL. LVII.]) PHILOSOPHICAL TRANSACTIONS. 397 



was entirely common air; consequently the air discharged from the Rathbone- 

 place water consisted of 84- oz. of common air, and about 66 of fixed air. The 

 air which was discharged before the water began to boil, contained much more 

 common air, than that which was discharged afterwards ; that which was discharged 

 towards the latter end seeming to contain scarcely any but fixed air. :lf 



As so much fixed air is discharged from this water by boiling, it seemed reason- 

 able to suppose, that the distilled water should contain fixed air. He accordingly 

 found it to make a precipitate with lime-water. 



Exper. 4. — The following experiment shows that the fixed air was not 

 generated during the boiling, but was contained in the water before. Into 30 oz. 

 of Rathbone-place water was poured some lime water, which immediately made 

 a precipitate. More lime-water was added, till it ceased to make any further 

 precipitate. It required 20-j- oz. The precipitated earth being dried, weighed 

 39 grs. 



The unneutralized earth contained in 30 oz. of Rathbone-place water is 16^ 

 grs., and the earth contained in 204^ oz. of lime-water (as was found by 

 precipitating the earth by volatile sal ammoniac) is 21 grs. Therefore the earth 

 precipitated from the mixture of Rathbone-place water, and lime-water, is about 

 equal to the sum of the weights of the earth contained in the lime-water, and 

 of the unneutralized earth in the Rathbone-place water; and consequently all 

 the unneutralized earth seems to be precipitated from Rathbone-place water by 

 the addition of a proper quantity of lime-water. But a more convincing proof 

 that this is the case, is that the clear liquor, after the precipitate had subsided, 

 did not deposit any earth on boiling, or become in the least cloudy on the 

 addition of fixed alkali; whereas Rathbone-place water in its natural state 

 becomes opaque by it. It might perhaps be expected, that the clear liquor should 

 still make a precipitate on the addition of fixed alkali, though the unneutralized 

 earth is precipitated; as in all probability there is still a good deal of earth 

 remaining in it in a neutralized state. The reason why it does not, seems to be, 

 that the remaining earth is most likely entirely magnesia; and Epsom salt, 

 when dissolved in a great quantity of water, does not make any precipitate on the 

 addition of fixed alkali. 



There is great reason to suppose that the earth, precipitated on mixing the 

 Rathbone-place water and lime-water, was very nearly saturated with fixed air, 

 i. e. that it contained very near as much fixed air as is naturally contained in the 

 same quantity of calcarious earth. If so, 30 oz. of Rathbone-place 

 water contain as much fixed air as 39 grs. of calcarious earth; whereas 

 the unneutralized earth, in that quantity of water, is only 164 grs. so 

 that Rathbone-place water contains near 24- times as much fixed air as is sufficient 

 to saturate the unneutralized earth in it. It seems likely from hence, that the 

 suspension of the earth in the Rathbone-place water, is owing merely to its being 



