On phlogiston. 383 



cr part of the air. Several of my late experiments con- 

 firm this. Indeed, the different degrees of the diminntion 

 of atmofpherical air in different proceffes, and in the dif- 

 ferent methods of conducing the fame procefs, is a full 

 proof of this. 



2. I find ivory black a more convenient fubftance for 

 the experiments recited in my paper than the black bones I 

 then made ufe of; firft giving it as much heat as I can in 

 a fmith's forge, without any accefs of air. It becomes white 

 not only when heated in atmofpherical air, but in phlogif- 

 ticated, or inflammable air, the quantity of which is there- 

 by increafed, by an addition of inflammable air. And that 

 this addition of inflammable air comes from the bones, and 

 from the principle that conftitutes their hlachiefs, and iiot 

 irom any decompofition of the -water over which the pro- 

 cefs is made, is evident from that water containing no aci- 

 dity, and its yielding air lefs pure than before ; whereas, 

 had the water been decompofed, fmce it is faid that 85 

 parts in 100 are oxygen, it mufi: have been found in the 

 form either of an acid, or of pure air. That it is not con- 

 tained in the bones, is clear from their receiving no addi- 

 tional weight. 



3. The fame thing appears to me to be proved by the 

 heating of ■zinc. When this is done in atmofpherical air, 



jlo^jcers of zinc are produced, and the air is diminillied. 

 After this the air is increafed by the addition of inflamma- 

 ble air; and inftead of flowers of zinc, a black powder is 

 fubliraed. If the water be decompofed in this procefs, 

 where is the oxygen that muft be difengaged at the fame 

 time Vv'ith the hydrogen ? It is not in the water, or the 

 black powder ; for this appears to be nothing more than 

 zinc fublimed. It becomes white when it is heated in 

 common air, and diminiflies it. 



4. Both iron and zinc, efpecially the latter, give out 

 much inflammable air in pure water ; and yet that v/ater 



acquires 



