04 Mr. D. Waldie's Experimental Researches 



Combustion of coal gas in mixtures of 



Sp. gr. 

 Permitted. Prevented. IIydrog.-=.\. 



1 Oxygen... 7 8 Nitrogen 14<'12 



1 Do. ... 3 4 Muriatic acid ... 18-4.2 



1 Do. ... 2i 3 Carb. acid 22-12 



1 Do. ... 2 2i Fluosilic acid ... 52-72 



Now we observe that their power of preventing combustion 

 is just in the order of their density. Sulphurous acid was 

 also tried, but it was found to hold about the same place that 

 muriatic acid did, which it should not do, as it is denser than 

 carbonic acid, itssp.gr. being 32-1 (hydrog. = 1). It ap- 

 pears, however, that it is decomposed when there is more 

 than a certain proportion of oxygen present to invigorate the 

 combustion ; as on inspecting the flame the external blue shell 

 of flame, where the principal combustion takes place, was 

 found to be enlarged and considerably .stronger in colour, 

 and a red streaky appearance was also observed in the flame, 

 precisely similar to that observed in the flame of sulphuretted 

 hydrogen, from separation, I believe, of particles of sulphur ; 

 this being in accordance with the fact, that hydrogen and 

 carbon at a temperature of ignition decompose sulphurous 

 acid. 



Sir Humphry Davy tried the effect of various mixtures of 

 gases in preventing the explosion of oxygen and hydrogen, 

 a table of which he has given. To many of these this ex- 

 planation does not apply, as the greater part of those he em- 

 ployed were combustible gases ; and there is most probably 

 in that circumstance other causes affecting the result, only to 

 be avoided by employing incombustible gases. He has 

 noticed, however, that a wax taper is extinguished in air con- 

 taining yo^^ °^ silico-fluoric and ^th muriatic acid gas ; also 

 that a larger quantity of steam is necessary to prevent the ex- 

 plosion of oxygen and hydrogen than of nitrogen. This 

 latter fact is usually connected by chemical writers with the 

 heat necessary to maintain steam in the state of gas, but 

 it appears rather to be one instance among the others fol- 

 lowing the general law; that, of ijicombustible gases 'which 

 remaiti undecomposed the ponxter of preventing combustion is in 

 the order of their density: what the exact ratio is I cannot at 

 present say, but beginning with steam, which has a sp. gr. 

 ss 9. (Hydrog. = l)j we have the gases increasing in this 

 power in the order already given in the table, namely, nitro- 

 gen, muriatic acid, carbonic acid, and fluosilicic acid. The 

 vapour of anhydrous sulphuric acid, sp.gr. = 40*1, should 

 stand between the carbonic and fluosilicic acids, if no decom- 



