Oafious'Oxydof Carhtn. iSy 



<;(muc£tecl with a pneumatic ap}>aratus, to a red heM5a qua«i-^ 

 titv ot'n, gas conies over which biirus in a manner finnlATto 

 <he hydrocarbonats. It conlills of about one part of car- 

 bonic acid and fix parts of a fpecies of inftanimabk gas whklb 

 Dr. Prieftley confiders as a fnecies of hydrocarbonat. 



A mixture of oTav ox yd of iron (fGrgc-fcales) and carbon at 

 «f barytesby (Inrilar treataient gives alfo .an inflammable gas, 

 which Mr. Cruickfliank finds to confill of car^jonic acid gas 

 i\- parts, and gafeous oxyd of carbon one part, 



Mr. Cruickfhank obtained a (imilar gas from -mixtures of 

 charcoal and ful)Hmcd oxyd of zinc, red oxyd of cop^Tier, ii- 

 tbanre, nianganefe; and concludes, that all tnetalli^ oxyd^ 

 capable of enduring a red heat, being treated with charc(xal,- 

 «^'ill yield not only carbonic acid buta fpecies 'of infiamttiaHe 

 gas ; that the oxyds which retain their oxygen moH obfti-- 

 nately yield molt inflammable gas, and ihofe vvliich part wit-h 

 it readily mod carbonic acid. The latter comes wer ^-biefly 

 at the beginning, and the inflammable gas towards the conelu- 

 fion of the proccfs. 



Mr. Cruickihank, having repeatedly wafhed this inflaJai'- 

 mabie air with lime water to feparatc the carbonic acid, foiisaxi* 

 it to be only a very little lighter than conunon air, that is to 

 faV; in the proportion of about 22 to 23 5 the common hydro^- 

 carbonats are not more than half that weight. Having eii— 

 deavoured to eftimate the quantity of pure oxygen ncc^ilary^ 

 io faturate it, after feveral trials he foiuid that four nteaftue;? 

 of it and t>vo of oxygen, exploded in a ftrong glafs jar over 

 mercury by means of the eleolric fpark, were reduced to 3.^, 

 which by agitation with linie water were proved to be car- 

 bonic acid, except about -i of a meafure which, by the nitrous 

 tell, was pure oxygen : hence it would appear that eight 

 meafurcs of the gas require 3^; meafures of pure oxygen gas 

 to faturate them, aiul produce by their crjmbination fix mea- 

 furcs of carbonic acid gas* with a little water. Six meafurcs 

 of carbonic acid gas require for their production at lead feveit 

 meafurcs of pure oxygen inftead of 3 [, the quantity made ufe 



'^ Hydro-carbonats mixed with oxygen and cxpluded, are increafcd in 

 volunje yiftead of h-S\v\g dimin'lbcd^ as is rhe ^fe with xhh gafeous oxyd. 



