A,!^ EXPERIMENTS AND OBSERVATIONS ON THE 



Seguin's eudio- The eudiometer with phofphorus, as recommended by Seguin, 



Torus'^objedk/'^^ ^^' "° "^^^"^ ^^^^ ^'■°'" ^''^'^ difadvantages. It is fubjea to 

 to J the fame inconveniences as the nitrous gas, with refpeftto the 



frequent change of vetTels; and, if we may credit the ob- 

 fervations of V. Humbold, is liable to feveral fources of 

 fallacy from the different proportions of oxigen, which the 

 phofphorus abforbs, and from its combining alfo yvilh nitrogen. 

 A portion of carbonic acid may alfo be generated, if the phof- 

 phorus be not perfediiy free from impurities. The eudiometri- 

 cal tefl, which has been lately recommended by Davy, viz. 

 and alfo tjie im- a folution of the pale fulphate of iron, faturated with nitrous 

 phate of Davy. S^^' '^ ""^ altogether exempt from the inconveniences which 

 attend the ufe of the latter fubftance, and has the additional 

 objeflion, that a portion of nitrogen is generally difengaged 

 from the folution, after the abforption of oxigen is com- 

 pleted. 

 Sulphuret of , The fulphurds of alkalies and lijne have hitherto been re-- 

 abfolb oxigTn garded as among the mod accurate tefls of the purity of at- 

 veryflowlyj mofpherical air. They, however, abforb oxigen but flowly, 

 and feveral days may elapfe, before the abforption be com- 

 pleted. It is therefore, in general, neceflary to have recourfe 

 to complicated and uncertain calculations, in order to adjufi: 

 the refult of the experiment to the variations of the furrounding 



andarenotcom- atfjiufpiiere. To remedy this obied^ion to their ufe, the ap- 



pletely amended ,. - r ^ , r . i ^^ i i • ■ 



in this refped by P''cation of lieat was propoled by Guyton, by which means a 



heat. fpeedy abforption was effeded ; but, befides, that fume dif- 



ference of the product may refult from the method employed, 

 the apparatus itfelf is objeflionable, from its fize and in- 

 equality of dimenfions. 



The apparatus of Luckily for the progrefs of eudiometrical fcience, ihefe 



Dr. Hope aftords ^^fjacles to the attainment of an accurate knowledge of the 

 great advanta^;c. _ ■ t> 



conftituents of the atmofphere, fecm to be now, in a great 



meafure, removed, by the invention of an apparatus by 



Dr. Hope, which unites the advantages of neatnefs and fim- 



plicity with ihofe of extreme accuracy and expedition, and 



of which you have already given a very lull defcription in 



your Journal*. In the trials which I have made with this 



inftrument, the fubftance found to anfwer beft as a teft of the 



Snlphuretof atmofpherical air was ihe fulphuret of lime, which is more 

 Itme was ufcd. 



* Vol. VI. pages 61,210. 



readily 



