36 On the Composition of the Basic Sulphate of Mercury. 



formula S O a + 2 Hg O, which in the former work is quoted 

 on the authority of Barker and Gerger, neither of whom was 

 really the author of the analysis, which is a very old one by 

 Braamcamp and Siquiera Oliva, as Dr. Pereira in his excel- 

 lent work very properly states. 



Another much more modern, and better analysis, by Dr. 

 Phillips*, is quoted in Turner's Chemistry, and also by Dr. 

 Christison ; the formula deduced from it is 3 . S O a + 8 Hg O. 

 This analysis is very nearly correct, yet the slight error which 

 it contains has the effect of giving to the formula a complexity 

 which it does not properly possess. 



In Berzelius's System, and in Gay-Lussac's Chimiedes Sels t 

 the formula given is S 3 + 3 Hg O. This I have found to be 

 the true composition of the salt, and it is adopted by Graham 

 in his Elements; yet I have never been able to find in the 

 Journals the analyses on which it is founded ; hence I consider 

 that the details of those by which I satisfied myself of its cor- 

 rectness may have some interest to chemists. 



A. 6*503 grammes of perfectly dry and neutral sulphate 

 of the red oxide of mercury were boiled for a long time with 

 much water, and the yellow powder which formed was col- 

 lected on a tared filter, and having been dried until it ceased 

 to lose weight, was found to weigh 4*623 grammes, or 71*09 

 per cent. 



The filtered liquor contained mercury. It was treated with 

 sulphuretted hydrogen, and the sulphuret of mercury which 

 fell was found, when perfectly dry, to weigh 0*706 or 10*85 per 

 cent., corresponding to 10*11 of oxide of mercury. 



The excess of sulphuretted hydrogen having been expelled 

 by boiling, the sulphuric acid in the liquor was thrown down 

 by nitrate of barytes. The sulphate of barytes weighed 3*607 

 or 55'5 per cent., containing 19*08 of sulphuric acid. Of this 

 3*71 had been united to 10*11 of oxide of mercury, forming 

 13*82 of sulphate of mercury which had not been decomposed 

 by the water. Hence there had been decomposed 86*18 per 

 cent, of the sulphate, yielding 15*37 of sulphuric acid and 

 71*09 of turpeth, indicating thus a slight excess of weight, 

 owing probably to the turpeth not having been rendered ab- 

 solutely dry. Hence 100 parts of the neutral salt, if perfectly 

 decomposed, should give 



17*67 of sulphuric acid, 

 82*49 of turpeth mineral. 



100*16, showing a slight excess, as above noticed. 

 Now as 100 of neutral salt contains 73*17 of oxide of mer- 

 * Phil. Mag. Second Series, vol. x. p. 206. 



