156 RESEARCHES UPON THE CHEMICAL PROPERTIES OF GASES. 



Thallium iodide 439° 



Lead chloride 498° 



Silver bromide 527° 



Potassium iodate 582° 



Barium nitrate 593° 



(Laiidolt and Bornstein's Tables and J. Cli. Soc, 1888, p. 63.) 



The following general method was used in studying oxidation temperatures of 

 hydrocarbons : 



Air containing- a small measured percentage of the hydrocarbon was agitated 

 with caustic soda solution to remove carbon dioxide. It was then caused to flow 

 through the bottle (G) containing lime water. This served to show whether the gas 

 had been completely freed from COo. The gas then traversed the palladium asbestos, 

 or other reagent contained in the glass tube in the oven, and finally a second bottle 

 of lime water (H). On heating the oven, the temperature of oxidation of the hydro- 

 carbon could be recognized by the precipitate of carbonate of lime in the second 

 lime water bottle. As an indicator for COo in the oxidation experiments, solutions 

 of baryta strontia and lime were all tried. The solubilities of the carbonates, accord- 

 ing to Fresenius, are as follows : 



BaCOg one part in 14,137 parts water. 



SrOOj " " "18,045 " 



CaCOa " " " 10,601 " 



Baryta water appears to be the most delicate test. On account of its extreme 

 sensitiveness, however, it is not easily preserved free from turbidity, and lime water 

 was found sufficiently sensitive for almost all purposes. The same general method 

 above detailed was used in all the following experiments. 



It seemed desirable at the outset to test the question, Do the hydrogen and car- 

 bon of a hydrocarbon burn simultaneously ? 



In the oxidation of a hydrocarbon in presence of excess of air, it seems probable 

 that the hydrogen and carbon must burn simultaneously to HoO and CO2. It is 

 possible, however, that under the conditions above described a selective oxidation of 

 hydrogen might occur, involving the formation of a condensation product. 



Thus CH^ might yield acetylene : 



2 CII, + O3 = 3 HjO + C.,!!., and no CO,. 



3 CII^ might yield C^II^ ; 



2 CH, + 2 = CjH, + 2 H,0 and no CO,. 



As reagents for the detection of moisture in a gas, the following substances 

 were tried: 



Anhydrous cobalt chloride, anhydrous copper sulphate, phosphoric anhydride, 

 a mixture of green vitriol with ferricyanide of potassium, the green vitriol being in 



