400 THIRD REPORT — l8oS. 



cases the numbers given by experiment cannot be reconciled 

 with the hypothesis. The following are the numbers which he 

 is disposed to believe very nearly correct: — lead, lOo'G; silver, 

 108; chlorine, 35'42; barium, 68"7 ; mercury, 202, perhaps 

 slightly higher, but not higher than 202-o ; nitrogen, 14*2. Dr. 

 Turner states that his methods for ascertaining nitrogen were 

 not so advisable as that in which Dr. Prout is occupied by 

 weighing the gases. This weight should be kept in abeyance 

 for the present. He conceives that it does not fall below 14, 

 nor exceed 14'2. During these researches he incidentally ob- 

 tained some facts for inferring the equivalent of silver ; and 

 from these it appears that the equivalent of sulphur is nearer 

 16" 1 than 16. He would not venture, however, to make a 

 positive statement without further inquiry. 



He then mentioned that Dr. Prout had kindly informed him 

 of a fact which he conceived analytical chemists in general to be 

 ignorant of, and which he thought might have had an influence 

 on these researches. The fact is, that chloride of silver, however 

 white and well washed, gives out a little muriatic acid at the 

 moment of fusing. This fact Dr. Turner has examined, and can 

 confirm. It especially ensues when fusion takes place before 

 the chloride has been well dried ; but in the event of the chloride 

 of silver being first well dried at 300° (when no acid is given 

 out), and then, without exposure to the atmosphere while cold, 

 fused, the loss of acid is not appreciable in weight, though it is 

 still sufficient to redden delicate litmus paper. In two experi- 

 ments about fifty grains of chloride of silver were fused, (pre- 

 viously dried at 300°, introduced while hot into a dry bottle 

 furnished with a tight cork, and weighed in that state,) and the 

 loss was inappreciable. From this circumstance, taken in con- 

 junction with the mode in which he habitually weighs the 

 chloride of silver, he is satisfied that the fact observed by Dr. 

 Prout does not necessarily produce any error in the determi- 

 nation of chlorine by means of silver. 



Notice of a Method of analysing Carbonaceous Iron. By 

 Professor Johnston. 



Professor Johnston gave an account of a new mode of deter- 

 mining the amount of charcoal in the carbonaceous irons, by 

 which he hopes to obtain results more precise and trustworthy 

 than those arrived at by any former mode. This method con- 

 sists essentially in reducing the iron to fine powder in a steel 

 mortar, and burning it with oxide of copper. Mr. Johnston 

 expects to be able to lay a series of results before the next 

 Meetine of the Association. 



