86 On definite Proportions. 



is of little consequence, I have assumed throughout this 

 Essay, for the component parts of the sulphate of baryta^ 

 Sulphuric acid 34 100 



Baryta 6Q )g4 



If we took a mean of the six experiments which have 

 been related, giving 118-627 of sulphate of baryta for 100 

 of carbonate, the proportion would become 



Sulphuric acid 33-9 100 



Baryta ...... 66-1 19.5 



Klaproth obtained, from JOG grains of carbonate of baryta, 

 120 of dry sulphate, and Bucholz n9f, which were re- 

 duced by ignition to 117. Hence Klaprolh calculated that 

 the salt consistt'd of 33 acid and 67 base, Bucholz 32'48 

 and 67 "32. They both employed precipitation and filtra- 

 tion. In the process of filtration it is scarcely possible to 

 avoid loss, and the diflerent degrees of moisture in the 

 filler cause great uncertainties in its weight, since it cannot 

 be weighed hot in a good halance, without giving a result 

 considerably too small. I have therefore avoided this pro- 

 cess as much as possible; but where it was indispensable, 

 I have employed English copyinti paper, made for Watt's 

 patent machmes, which I have previously washed, and 

 dried in as strong a heat as it could support without burn- 

 ing. The largest filters that I have used weighed less 

 than '75 gramnic, and their weight has never varied more 

 than •0<;C) gr., nor even so much, unless they were left 

 very long in the scale. The smaller ones, which weiglied 

 from '1 to "25 gr. have never varied perceptibly. I have 

 removed the mass lying on the filter, without scraping off 

 the smali quantity which was firmlv attached to it ; and 

 having weighed and ignited that which 1 had removed, I 

 have computed the diminution of the whole quantity by 

 the operation. 



Bucholz (Scher. X. 385,) boiled 100 grains of sulphur 

 with aqua regia, until it was converted into sulphuric acid, 

 from which he obtained 724 gr. of stiiphate of baryta; 

 and hence, according to his determination of the compo- 

 sition of this salt, it follows that 100 pp.ns of sulphuric 

 acid contain 49'5 of sulphur. According to my analysis, 

 these 724 grains contain -MG\6 of the acid; giving 146*!6 

 of oxygen to icO of sulphur; and, for 100 of the acid, 

 40 624 of sulphur and 39-376 ol oxygen. Bucholz's 

 txptrinent therelore agrees with 'mine, within -00044. 

 Buch,)lz employed sulphur which had been kept long 

 melted in a strong heat ; mine was ignited in combination' 



with 



