178 



Thenard's 

 mode of ascer- 

 taining the 

 composition 

 im perfectly 



given. 



Berthollefs 

 experiments 

 not given. 



Mr. Chenevix 

 more particu- 

 lar. 



His process. 



ANALYSIS. OF SULPHATE OF BARYTES, 



means of finally deciding the question. In the extract, 

 which Guyton has given of the memoir of Thenard on the 

 different states of antimony, in the 32d volume of the An- 

 nates de Chimie, the mode in which he ascertained the 

 composition of sulphate of barytes is not stated with suffici- 

 ent minuteness, to enable any one to repeat his experiment. 

 One hundred grains of pure barytes, fused in a crucible, 

 are stated to have afforded 133*3 grains of calcined sulphate 

 of barytes ; but whether by direct combination, which 

 would be liable to errour, or through the medium of some 

 other solvent, is not mentioned. Nor is the mode by which 

 the pure barytes was obtained noticed in Guyton's extract, 

 though of the utmost importance in this inquiry. The 

 experiment indeed does not appear to have been made in a 

 way favourable to accuracy and precision, though for 

 want of sufficient details it is not possible satisfactorily to 

 point out the sources of errour. The experiments of Ber- 

 thollet, which determined the proportion of acid in sul- 

 phate of barytes at 27 per cent, 1 am wholly unacquainted 

 with ; nor do I know the mode which this celebrated che- 

 mist pursued in making them ; which I regret the more, as 

 they are stated to have been conducted with scrupulous 

 exactness. 



Mr. Chenevix's paper in the Memoirs of the Irish Aca- 

 demy however contains all the details necessary for the ex- 

 amination of his experiments, and fortunately also furnishes 

 additional proof* of the accuracy of my own results. 



To ascertain the quantity of sulphuric acid in sulphate 

 of barytes, Mr. Chenevix decomposed a given weight of 

 sulphate of lime (the composition of which he had ascer- 

 tained by previous experiments); and haviug found the 

 quantity of sulphate of barytes, which it afforded, the pro- 

 portion of sulphuric acid in the latter was readily deduced. 

 ." Upon 100 grains of calcined sulphate of lime," says 

 .Mr. Chenevix, '• I poured some oxalic acid, which attracts 

 the basis with an affinity superior to that exercised by sul- 

 phuric acid. Oxalate of lime was here formed, but oxa- 

 late of lime is soluble in a very small excess of any acid. 

 A little muriatic acid operated a complete solution, and 



thu* 



