342 On dejinile Proport'ioni. 



iHiiphuret was powdery, and dark gray, without mefallic 

 liir^irc. I at first attributed this to impurities in the lead which 

 " J then employed ; but T afterwards found that it'depended on 

 the presence of hyih'ogen. I had mixed ten granmies of re- 

 cently prepared sulphuret of lead wirh 40 jrr. of ignited 

 oxide of tin, aiu!' heated the mixture in a small glass retort ; 

 Jience f obtained, with some sulphurous acid gas, a few 

 drops of water. The same happened a second time; and 

 as 1 had the instant before ignited both the substances, and 

 liad itiixcci them while still hot, the water could be derived 

 from no other source than from hydrogen in the sulphuret. 

 ill fact, when I i^niled some sulphuret of lead which had a 

 metallic lustre, and had been ))repared in a white heat, to- 

 gether with some oxide of tin, I obtamed only a very slight 

 trace of water, which clouded the neck of the retort. 



I was hence induced to make some experiments on the 

 hydrogen contained in sulphur. In these experiments it 

 was observed, that most powdered substances, which I had 

 freed from moisture by ignition, when they were again ex- 

 posed to the open air, and then, without any alteration of 

 the moisture or tetnperature of the atmosphere,' after some 

 hours a»;ain ignited in a small glass retort, nfiordtd some 

 water in the neck of the retort, which however was only 

 extricated after the temperature had been raised far above 

 the boiling point. Hence it is very difficult in such ex- 

 periments to avoid the moisture, which adheres mechani- 

 cally to the substance, and which always makes the result 

 somewhat too great. 



Five grammes of sulphur, which had before been dried 

 by fusion over a spirit-lamp, were mixed with fifty of the 

 ignited protoxide of lead, and exposed, in a small glass re- 

 tort, to a temperature which was gradually raised. The 

 retort was furnished with a small receiver, out of which the 

 sulphurous acid gas was conducted into a glass tube, lilled 

 with njuriate of hme. When the retort had been ignited 

 for half an hour, it had lost '9 gr. in weight, while the re- 

 ceiver had gained "157. The water in the receiver was 

 tasteless, and had a slight sulphureous smell. Hence the 

 sulphur in this experiment had afforded 3*15 per cent, of 

 water. It could not have contained the whole of this 

 quantity as adhering moisture, havinji been previously in 

 fusion: and the water must have been formed from the 

 hvdrogen in the sulphur and the oxvgen of the protoxide 

 of lead. There remained in the retort a mixture of sul- 

 phate of the protoxide and sulphuret of lead. The quan- 

 tity of water obtained indicates somewhat less than '4 per 



cent. 



