2yG Analysis of Wackt, 



Earthy phosphate of iron has recently been found at Hop- 

 kinton, Mass. It exists there in large quantities, and is em- 

 ployed as a pigment. The gentleman on whose grounds it 

 was found sent me several pounds of it. 



J. F. D. 



Art. XVI. Analysis of Wacke, by Dr. J, W. Webster, 

 of Boston. 



V/NE hundred parts exposed to a red heat in a platina cruci- 

 ble lost 18.6, acquired an umber brown colour, and a degree 

 of hardness sufficient to scratch glass. 



One hundred parts reduced to fine powder were mixed with 

 four times the weight of soda, and exposed to heat, gradually 

 increased for three quarters of an hour ; at the expiration of 

 which time, the whole had acquired a pasty consistence. The 

 crucible was now removed from the fire, its outer surface 

 carefully wiped. Muriatic acid was poured on till all efferves- 

 cence ceased. The solution obtained was evaporated to dry- 

 ness, gradually assuming an orange red colour. Water was 

 now poured upon the mass, after which it was filtered, and the 

 powder remaining carefully dried ; after ignition, and while 

 warm, it weighed 28 parts. This powder was insoluble in 

 muriatic acid, and of a white colour. 



To the filtered solution, reduced by evaporation, carbonate 

 of potash was added, the precipitate was collected on a filter, 

 washed and dried ; it weighed 23. parts. This powder was 

 redissolved in sulphuric acid, sulphate of potash added, and 

 crystals of alum finally obtained ; hence this powder was 

 alumine. To the liquor from which the silex and alumine 

 had thus been separated, acetic acid was added ; the whole 

 evaporated to dryness ; the excess of acid being removed, a 

 small quantity of water was poured on, and after strong igni- 

 tion, the precipitate weighed 4.5. 



Into a very small tubulated retort I introduced a portion 

 from the same mass, whence the piece submitted to analysis 



