44 ON THZ DOCTRINE OF PHLOGISTON. 



to be employed, likewife hot and completely dried, the varia- 

 tions in the qualities of the gafes will be much lefs, the princi- 

 pal difference depending upon the proportions of tho carbonic 

 acid and the inflammable gafes j but the gafes from pure char- 

 coal, either alone or moiftened, never have any of the difiin- 

 guifhing characters of the gafeous oxide, being always much 

 lighter, yielding bulk for bulk when faturated with oxigen, not 

 more than one-third of the carbonic acid gas afforded by the 



the hydrocarbo- other. What, however, diftinguifhes them ftill more com- 

 ' Hghter than"he P* ete b r ' * s the large proportion of water generated by the 



gafeous oxide, combuftion of the hydrocarbonate in oxigen gas ; for the gaf- 



wate^by com- d eous ox ^ e wnen P ure ' or Durned under the fame circum- 

 buftion with ox- fiances, never produces the leaft fenfible quantity of this fluid. 

 jf r e r "* n In mentioning the circumftances of the production of the 



tation and re- gafeous oxide of carbon from the metallic calces and charcoal, 

 marks. & c . j) r . Prieftley has fomehow mis-ftated both the meaning 



and words in what he calls a quotation from the firft. paper ; 

 this paffage in his letter is as follows (fee p. 182.) : " After 

 " repeating my experiment, which he found to be juft, Mr. 

 M Cruickfliank did the fame with the calces of the other me- 

 " tals, as zinc, copper, &c." and then concludes (p. 4.) " that 

 te in all thefe cafes the air mufi come from the partial $ecompo- 

 " fition of the carbonic acid by the calx, when raifed to a high 

 " temperature :" Then the Dr. goes on and adds : «.« But the 

 " inference that I think is more naturally drawn from them is, 

 " that all thefe calces contain much water, and little or no- 

 " thing elfe." Now the paffage from which this quotation 

 appears to have been taken (for there is nothing in p. 4. ex- 

 actly fimilar to it), does not follow the account of the experi- 

 ments with the calces of the metals, &c. but is an inference 

 drawn from the firft experiments made with the carbonates 

 and the iron fcales. I fhall infert this paffage, and leave the 

 philofophical reader to judge for himfelf of the accuracy of the 

 ffatement and the juftnefs of the conclufion. " Conceiving 

 f that in thefe experiments * the gafeous oxide muft proceed 

 " from the partial decompofition of the carbonic acid by the 

 ** iron when raifed to a high temperature,. I thought I (hould 

 " fucceed better by employing iron filings in place of the grey 



* Aliuding to thefe made with the carbonate of barytes and iron 

 fcales, or imperfect grey oxide. 



4 ** oxide* 



