ON CALCAREOUS EARTH 249 



his 6th experiment. As the atmosphere always contains some 

 uncombined fixed air, what wonder that quicklime should 

 return in time to crude calcareous earth ? Putrid vapours 

 contain a far greater quantity of this fixed air, consequently 

 we know that phlogiston must be combined in the air with 

 some substance; for were it uncombined, so that it could 

 unite with lime (I very much question, however, whether 

 phlogiston can unite with pure lime), it would much sooner 

 combine with pure air, for which it has a very strong 

 attraction ; but we know that in this case the air becomes 

 unfit for respiration, and therefore the earth must have long 

 since lost its inhabitants. He thinks that the 10th experi- 

 ment is so clear and convincing, that no doubt can remain 

 respecting his new doctrine. But had he been better 

 acquainted with oils, he would not have looked on his 

 experiment as incontrovertible; for as the vitriolic acid in 

 sulphur fixes the phlogiston, even so does the fixed air in 

 oils fix the same principle. As when we mix lime with 

 sulphur, phosphorus, or regulus of arsenic, and afterwards 

 separate those inflammable bodies from the lime by burning, 

 and obtain in the first gypsum, in the second animal earth, 

 and in the third lime combined with arsenic ; so also must 

 lime, when linseed oil is burned with it, exhibit a combination 

 of lime and fixed air. With respect to the 13th experiment, 

 I can assure the author that iron dissolved in vitriolic acid 

 yields but very little fixed air ; the air is mostly inflammable. 

 The author must not then compare this with that air which 

 is extricated from chalk by acids ; for the inflammable air 

 is formed during the solution of the metal in vitriolic or 

 marine acid ; but fixed air is present beforehand in chalk. 

 That the air which is expired from the lungs carries along 

 with it fixed air, is absolutely certain, on which account 

 lime-water is precipitated by this air. Fixed air is actually 



