relating to JAr and Water, 299 



■Goiifrdermg how little this inflammable air weighs, vh, the 

 Avhole 1054 ounce meafures not more than 63 grains, and the 

 difficulty of afcertaining the lofs of water to {o fmali a ciuan- 

 tity as this, it is not poffible to determine, from a procefs of 

 this kind, how much water enters into the compoiition of the 

 inflammable air of metals. It would be more eafy to deter- 

 mine this circumflance with refpe6l to the inflammable air of 

 charcoal, efpecially by means of the experiment made with a 

 burning lens in vacuo. In this method two grains of charcoal 

 gave at a medium thirteen ounce meafures of inflammable air, 

 which, in the proportion of 30 ounce meafures to 8 grains, 

 will weigh 3.3 grains; fo that water in the compofition of this 

 kind of inflammable air is in the proportion of 1.3 to 2, though 

 there will be fome difficulty with refpe6l to the fixed air inti- 

 mately combined with this kind of inflammable air. 



Since iron gains the fame addition of weight by melting in 

 dephlogijllcated air, and alfo by the addition of water when 

 red-hot, and becomes, as I have alread)/ obferved, in all re- 

 Ipedlsthe fame fubftance, it is evident, that this air or water, as 

 exifting in the iron, is the very iame thing ; and this can 

 hardly be explained but upon the fuppofition that water confiils 

 of two kinds of air ; viz. inflammable and dephlogifticatedL 

 I (hall endeavour to explain thefe procefles in the following 



manner. 



■■♦■ 



When iron is melted in dephlogiflicated air, we may fuppofe 

 that, though part of its phlogifton efcapes, to enter into the 

 compoiition of the fmall quantity of fixed air which is then 

 procured, yet enough remains to form water with the addition 

 of dephlogiilicated air which it has imbibed, fo that this calx 

 of iron confiils of the intimate union of the pure earth of iron 

 aad of water ; and therefore when the fame calx, thus fatu- 



Q q a rated 



