198 On dejiniie Proportions, 



9.) In a repetition of this experiment, the increase of the 

 weit^ht oF the coj)per amounted to 2 G granjnies. 



Several other experiments exhibited a still greater iiv 

 crease of v\eight ; bat I do not panicnlarly descrilje ihem, 

 since the results are always soniew hat too great, and do n.it 

 pert'ccily a'.'ree, a circnmst;ince probahlv depending on an 

 oxidatior, vvliich the supeiflLtous b;uiphnr is incapable ot" 

 reducing. 



The lollowing exper'nncnt however de.'Jerves to be noticed. 

 I had i)ut thin laminated copper in a small retort with sul- 

 phur, some of the plaies projecting Itinci) beyond the 

 sulphur. When the'iemperature was raised until the cop- 

 per beor^n to unite with the sniphnr, the mass became 

 lieated, but was not ignited, because the sulphur was in 

 excess, and ihe projecting parts of the plates did not enten 

 into combination with the sulphur. When 1 continued to 

 increase the heat, the small retort became completely full 

 of sulphurous gas, and before the mass at the bottom of 

 the retort was ignited, the plates were inflamed, and burnt 

 with a very bright light, exactly as during combustion in 

 oxygen. The copper therefore condensed the gaseous sul- 

 phur with the appearance of fire. Since copper combines 

 also with solid sulphur with a similar appearance of fire, I 

 was desirous to know if the phaenomena could be derived 

 in this case also from condensation. I weighed therefore 

 the sulphuret of copper, which I had obtained, in water : its 

 specific gravity was 4-76, thai of ihe laminated copper 

 S'723, and that of the sulphur 1-99. Now four parts of 

 copper had absorbed one of sulphur; so that the niechani- 

 cal mixture of four parts copper and one sulphur is denser 

 than the chemical compound, in the proportion of one loi 

 •9124. The sulphuret had iherefcuc expanded, and almost 

 in the same proportion as tho laminated copper would have 

 done by fusion : cpnsequenily the change of bulk could 

 not be tlie cause of the appearance of lire. Whence then 

 were the matters of light and heat in this case derived ? 

 The case is evidently similar to that of the combustion of 

 carbon in oxygen, where the heat is intense, although the 

 carbon is expanded. When a piece of charcoal is ignited 

 in nitrogen, by being placed between the points of two wires, 

 which are coutiectcd with the opposite ends of a great Gal- 

 vanic battery, and it appears to the spectator to burn, the 

 phaenouienon is of aditicrent pature, and its cause may be 

 spmewhat diflferent. Sulphur is the most negative of all 

 ^niown bodiesj except oxygen, with respect to the metals : 



licnce 



