6 On definite Proportions. 



will naturally occur to every attentive reader without my 

 assistance. 



I. Lead and Oxygen. 



Lead, as is well known, aflTords three oxides. In order 

 to ascertain the proportion of oxvgcn contained in them, 

 I employed lead which was obtained by the reduction of 

 the crystallized nitrate, and which was consequently free 

 from any mixture oi' copper or silver. 



A. Ytllow Oxide of Lead. 



1.) Ten grammes of lead were dissolved in pure nitric 

 ^cid, and in order to avoid loss, the process was performed 

 in a flask or receiver of glass held in an inclined position. 

 The solution was poured into a weighed dish of platina, 

 carefully evaporated, and exposed to a red heat. It afforded 

 ?.0"77 grammes of oxide. 



2.) The experiment was repeated, but the evaporation 

 and ignition were perfornied in the same vessel which 

 served" for the solution. The result was 10-775 grammes 

 of oxide of lead. 



3.) In a tliird experiment a flask with a long neck was 

 employed. When the salt began to he decomposed, a 

 small quantity of a mealy sublimate attached itself for an 

 instant to the neck of the vessel, and the vapours had not 

 the smell of a perfectly pure nitric acid. When the flask 

 had been heated throughout its whole length, the weight 

 of the oxidated lead amounted to 10-78 grammes, or a little 

 more than in the former experiments ; and at the same 

 time an appearance had taken place in this experiment, 

 which showed that a small portion of the oxide of lead was 

 carried ofl'wilh the vapour of the acid which was expelled. 



4.) Ten grammes of lead were dissolved in nitric acid, 

 and precipitated by carbonated ammonia : the precipitate 

 was placed on a weighed filler and well washed. It 

 amounted to 12-9025 grammes of carbonated lead. Of 

 this 12'77 a;ramnies were ignited in a dish of platina; the 

 residuum was 10-64 gr. of yellow oxide of lead, giving 

 10-75 for the whoU: quantity; so that 100 parts of lead 

 had taken up 10-75 of oxygen. I conceived a suspicion 

 that the carbonated an:monia might not have thrown down 

 the whole quantity of lead ; I therefore passed sulphurated 

 hydrogen through the liquor of precipitation, and through 

 the water with which the precipitate had been washed; but 

 thev were not rendered turbid bv it in the slightest degree. 



5.) Th« 



