150 ANALYSIS OF ADHESIVE SLATE* 



Roa&ted. d. A thousand parts of the mineral roasted in a retort 



yielded 270 of carbonic acid. 

 Di'^solved in e. Anpther thousand parts dissolved in ten times their 



rouriaiic acid, ^gig^^ ^^ muriatic acid lost 270 parts. 



It contains therefore 27 per cent of carbonic acid. 



I afterward proceeded with the analysis in the following 



manner. 

 Treated with 1. One part of the mineral was well powdered, and put 

 sulphuric acid, jj^^^ ^Q^j. parts of concentrated sulphuric acid, in which it 



dissolved with evident effervescence; and the solution was 



evaporated to dryness. 

 ^., , 2. The residuum was diffused in water, and a gelatinous 



matter separated, which was still a little yellowish. This was 



silex. 



3. The liquor was filtered. 



4. The gelatinous residuum was washed with boiling 

 water, till no farther trace uf sulphuric acid was discover- 

 able. 



5. This water and the filtered liquor were evaporated to- 

 gether, till there remained but ten drachms. 



lime. 6= Some sulphate of lime separated, which was decom- 



posed by an alkaline carbonate ; and after it had been 

 heated and roasted 0'08 of pure lime were obtained. 

 Iron and mag- 7. The liquor separated from the sulphate of lime was 

 ^'^^^' concentrated by heat, and it yielded crystals of sulphate of 



iron, and of sulphate of magnesia. 



8. Without separating the crystals T put the whole into 

 a platina crucible, and exposed tli^ saline mass to a strong 

 heat for two hours. 



9. After cooling, the mass had an ochry colour, and a 

 bitter taste. On it I affused boiling water, filtered and 

 washed the residuum. 



lion^ 10. The oxide of iron remained on the filter. After 



having been dried and roasted it weighed 0*09. 

 Magnesia. 11. I added to the liquor carbonate of ammonia, when a 



white earth was precipitated, which dried and roasted ap- 

 peared to be magnesia, and weighed 0*28. 



12. The yellowish gelatinous residuum (No. 4) was di- 

 gested in muriatic acid, till its colour became entirely white. 

 M<;re iron. 13. Being filtered and washed, the liquor was of the co- 



lour 



