On definite Proportions. 348 



cent, of hydrogen in the sulphur. Since this quantity of 

 hydrogen bears no proportion to that which is contained 

 in sulphuretted hydrogen, it can only be considered as aa 

 accidental impurity, arising from the mode of preparation 

 of ihc sulphur, and inseparable either by fusion or by 

 sublimation. It appears therefore to be unnecessary to 

 consider sulphur, according to the ingenious hypothesis of 

 Davy, as a triple combination of sulphur, hydrogen, and 

 oxygen ; for, if this idea were true, the quantity of hydrogen- 

 contained in sulphur would be required to be expressed bv 

 a number obtained by dividing the hydrogen of sulphuretted 

 hydrogen by 2, 4, or at mo^t S3 which however is not the 

 case, 



B. Protoxide of Lead. 



Since the composition of the protoxide of lead has served 

 as the foundation of most of my computations, I have 

 endeavoured to examine this body with the greatest possible 

 accuracy in the continuation of my experiments ; 1 have 

 not however been able to remove every difficulty, even after 

 the repetition of the experiments which are now to be de- 

 scribed. ! 



I dissolved 25 grammes of the same purified lead, which 

 I had employed in the experime:its above described, in a 

 glass flask, in pure nitric acid; I dried the solution in the 

 flask, and ignited the salt carefully, luitil the air which I 

 drew out of the ignited flask with my mouth through a 

 Jong glass tube, no longer contained any nitrous vapour. 

 The flask had now acquired an addition of 96-925 gr. in 

 weight : consequently the experiment confirms the first of 

 the former series relating to the composition of the prpt- 

 oxide of lead, and shows that this protoxide consists of 

 Lead.. 92-85, 100-0 1298-7 



Oxvgcn 7-15 7-7 1000 



From other calculations, I think I may venture to assert, 

 that if tliese numbers represent the quantity of oxygen as 

 somewhat greater than the truth, it cannot still be less than 

 7*633 for, 100 of lead. It is unfortunate that the bodies 

 which are the best adapted to afford foundations for compu- 

 tation, take up the smallest quantity of oxygen, so that any 

 unavoidable inaccuracy in the experiments made with them 

 is proportionally of the greater consequence. 



I have therefore possibly been in an error when I have 

 »et down the oxygen in the protoxide of lead as very pre- 

 cisely equal to half the quantity of sulphur which saturates 

 the same lead. 



Y4 C. SuU 



