•fHfi ACCOMPANYING SUBSTANCES. 19 



The folutions which I ufed, of all the above falts, were in 

 the moft concentrate Hate; therefore, in the ftate moft fa- 

 vourable for mowing precipitation, if any had taken place. 



It is not very difficult to account for the appearances that Caufes of the 

 deceived Mr. Guyton in his experiments, and for the caufe p^j^s 1S e * 

 that produced them. In one inftance, he obtained a precipi- 

 tate from muriate of lime and of alumina, becaufe, in all pro- 

 bability, the alumina he diffolved in muriatic acid had been 

 precipitated from alum ; and alumina, thus prepared, retains 

 a fmall portion of fulphuric acid *. In the next place, it is 

 very likely that his folutions were fufficiently concentrate to 

 give a precipitate of fulphate of lime. The tame was the 

 cafe with regard to his mixture of muriate of ftrontia with 

 muriate of alumina. As to the general conclufion, that ba- 

 rytes has an affinity for lime, magnefia, and alumina, which 

 ftrontia does not appear to pofiefs, it is to be explained as 

 follows. Lime often contains a little fulphate of lime. Mr. 

 Guy ton's magnefia, as well as his alumina, had probably been 

 obtained from the fulphate ; and we are indebted to Mr. 

 Berthollet, for the true nature of many fimilar precipitates. 



Barytes is a much more delicate tell than ftrontia, for ful- 

 phuric acid ; and therefore, barytic folutions were affected by 

 quantities of fulphuric acid, which ftrontia could not render 

 fenlible. This I have afcertained to be the cafe : for I have 

 obtained copious precipitates, by barytes, in a liquor com- 

 pofed for the purpofe, wherein ftrontia did not produce the 

 fmalleft cloud, or (how the prefence of fulphuric acid. 



A little care and attention are neceffary, in preparing the He did not take 

 earths, which are to be diffolved in the muriatic acid, f or due , car ^J n P r e- 

 thefe experiments; and, if Mr. Guyton had taken the requi- earths, 

 fite precautions, he would not have been led into error. The 

 object to be kept in view is, to free the earth from fulphuric 

 acid; and, if this be obtained, there is not the fmalleft pre- 

 cipitate or cloud, in any of the cafes I have mentioned. If 



* It is fomewhat fingular, that Guyton mould have obferved this 

 fact elfewhere. See his experiments on the diamond, in the Annates 

 de Chimie. The preparation of a barytic fait, by alumina prepared 

 from the fulphate of this earth, had been obferved by Scheele, in 

 his EJfay on the Affinities of Bodies. But that great chemift referred 

 the phenomenon to its right caufe, viz. to fgme fulphuric acid re- 

 maining in all alumina thus prepared. 



C 2 any 



