34 



solved out by alcohol, and may be obtained alone by evaporating the 

 solvent. 



Although collateral matter has been carefully excluded from this 

 paper, I cannot refrain from remarking that the property of clay 

 here mentioned is in fact the announcement of a new property of 

 soils, and one which will help to account for the formation of many 

 natural metallic sulphides. I hope soon to have some investigations 

 of this subject ready for publication. 



To ascertain whether this property of breaking up a sulphurized 

 compound in purified gas and removing tar was possessed by clay 

 alone, or shared by other substances used in purification, some puri- 

 fied gas was passed through a considerable chemical excess of all 

 the substances employed in purification, viz. lime, precipitated per- 

 oxide of iron, sulphate of iron, chloride of calcium, and dilute sul- 

 phuric acid, all but the lime being mixed with moist sawdust. Upon 

 passing the gas next through a purifier filled with clay, it darkened 

 lead-paper, and aifected turmeric when it had passed a subsequent 

 purifier filled with lime. This proves the power of clay to break up 

 one or more sulphurized compounds which no other substance used 

 in purification eifects ; and if this sulphur were not liberated from 

 the impure naphthalin compound already mentioned, it seemed cer- 

 tain that gas which had been previously purified by clay might be 

 much improved, if not rendered pure, by a removal of the sulphur 

 of the naphthalin. There is strong experimental evidence that the 

 compound from which clay liberates sulphide of hydrogen is not the 

 sulphurized naphthalin one ; for if hydrogen be passed through a 

 vessel containing this substance, then through clay, and subsequently 

 over lead-paper, no trace of sulphide of hydrogen is found, though 

 the gas passing smells strongly of impure naphthalin. This gas and 

 vapour burn with a lightless flame. Subsequently some naphthalin 

 was heated to ebullition, and a current of hydrogen sent through it 

 and then burnt. The flame was lightless as before. I mention 

 this fact to remove the popular error that naphthalin, as it exists in 

 coal-gas, is a good illuminant. Even Dr. Frankland thus regards it ; 

 and both in Clegg's book on coal-gas, and in the new edition of 

 lire's Dictionary, states that the hydrocarbons in gas are valuable in 

 proportion to the carbon they contain, and that naphthalin is the 

 most valuable as containing the largest proportion of carbon. The 



