On defirAte Proportions. 83 



phur of the sulphuret iiad been sufficient to form so much 

 sulphuric acid, as was necessary for neutrahsing the oxide 

 of lead. 



2.) In a second experiment the residuum weighed 12"6t 



3.) The experiment was ajain repeated in a glass retort 

 with a receiver, and the acid which passed over was poured 

 back and distilled once more from the mass in the retort. 

 The last part of the produr I was kept separate, but it af- 

 forded no perceptible trace of sulphuric acid ; consequently 

 the oxide of lead was sufficient to saturate all the acid 

 which was formed from the sulphur of the sulphuret. 



Hence I conclude, that since the sulphuret of lead con- 

 tains its constituent parts precisely in the proportion, 

 which is necessary for the formation of the sulphate, the 

 oxide of lead must contain exactly half as much oxyeeu 

 as the sulphuric acid contains sulphur. Probably the same 

 rule holds good for the combination of sulphur with other 

 combustible bodies : hence it will follow of necessity, that 

 the quantity of any oxide required for saturating a given 

 portion of sulphuric acid must contain half as much oxy- 

 gen as there is sulphur in the acid ; that is, if my experi- 

 ments on the oxide and the sul|>huret of lead have not 

 been completely erroneous. 



The quantity of sulphur in the sulphuric acid may be 

 easily determined from these experiments. Ten granimes 

 of the sulphuret of lead having taken up 2-65 of oxygen, 

 •673 of this belongs to the St)31 of lead, the remaining 

 1-975 formed, together with l-34y of sulplmr, 3-324 of sul- 

 phuric acid. Consequently K.iO parts of sulphuric acid 

 consist of 4058 sulphur and 3942 oxygen. The second 

 experiment gives 40-7 and 59'3 : and 100 parts of the acid 

 would require for their saturation, according to the first 

 experiaient, 280-3, and according to the second, 281 of 

 the oxide of lead ; a degree of coincidence which can 

 Bcarcely be exceeded. 



In order to ascertain what dependence can be placed on 

 these results, it was necessary to examine the composition 

 of the sidphate of lead. 



a.) The 10-77 grammes of oxide of lead, obtained in the 

 first of my expernnents on the yellow oxide, were dissolved, 

 in the same dish, in nitric acid, and then mixed with sul- 

 phuric acid as long as any precipitate could be observed ; 

 and afterwards dried and ignited. They alTorded 14-62 gr. 

 of sul|)hatc of lead ; consequently 100 parts of sulphuric 

 acid had combined with 280 of the oxide. 



^''2 I.) Ten 



