570 



'E-xpsrhnentS In the AtiaJyzntkn of Marl, Aygf; 



cafes may occur, it is plain that the real quality of the marl muft 

 be afcettained, by feparating all its component parts; for which 

 purpofe, the following procelTes were employed. 



1. ICO grains of the marl, taken from a portion previoufly 

 dried as above, were diiTolved in diluted muriatic acid. Care 

 ■was taken to allow the acid to be very (lightly in excefs. When 

 the efFervefcence ceafed, tlie whole was put into a filter, and 

 the undiflblved part fufhciently wafhed with diftilled water. 



2. The filtered folution was firft treated with cauftic ammonia, 

 which precipitated nothing. Ihe lime was therefore throw» 

 down bv carbonate of foda, and the n^ixture was boiled and fil- 

 tered. The filtered liquor being evaporated to a fmall quanti- 

 ty, and boiled with foda, a fmall quantity of lime was thrown 

 down. The two portions of carbonate of lime, thus obtained 

 after being properly wafhed, were dried, and then fubje£^ed to a 

 heat which caufed the Gdes of the crucible approach to rednefs. 

 They weighed together 74 grains. 



3. The undifTolved refiduum. No. i. was black, and, when 

 heated in a crucible, took fire as charcoal does. Being taken 

 from the furnace and allowed to cool, it weighed 23 grains. 

 After being fubjeded to a red heat for about half an hour, the 

 inflammable matter was confumed, and what remained, weigh- 

 ed 21 grains. Having been mixed with three times its weight 

 of dry^foda, it was kept red hot, in a filver crucible for an hour.. 

 The mixture was then reduced to powder, mixed with water, 

 and fuperfaturated with muriatic acid, in which the moft of it 

 was dilTolved. In order to obtain the filex which might be held 

 jn folution, the mixture was evaporated to drynefs; then diluted 

 with water, and digefted. It was then filtered. The filex re- 

 mained on the filter. After being waflied and heated r«d hot, it 

 weighed 14 grains. 



4. The folution which was filtered, had a greenifh coloun 

 Being faturated with carbonate of foda, and boiled for a little 

 time, a brownifh precipitate was thrown down. This, after be- 

 ing waflied on a filter, was digefted in a folution of cauftic pot- 

 afh. Some of it was diliblved •, but a brownifh matter remained, 

 apparently oxide of iron. The cauftic folution was faturated 

 with fulphuric acid, and a fmall quantity of argil was obtained, 

 which, after being heated, weighed 2 grains. 



5. The iron was powdered and put into diftilled vinegar, th^ 

 any lime or magnefia might be feparated. One grain of lime 

 was obtained. 



6. The iron was now moiftened with nitric acid, heated till 

 dry, and again treated in the fame way. It was then fubje£led 

 to a moderate heat during fifteen minutes, and afterwards di- 

 gefted 



