66 



EGYPTIAN HELIOTROPIUNl. 



inQh in thicknefs. It flrikes fire with fteel, a»d breaks into 

 acute angular irregular pieces. Its fpecific gravity is 2,708. 

 The llone is fold by the venders by the name of Egyptian Heli-^ 

 otrnpium. Its nature will be more clearly deduced from the 

 following examination : 



Anal^fis. 



/nilyfis. An entire poli(hed piece of the flone, weighing 250 grains. 



Ignition render- ^g^ expofcd to a white heat, in a wind-furnace, for two hours, 

 late brown, with and then fuffered to cool. The original green colour of the 

 white and yellow mineral, was changed daring this procefs to a chocolate brown, 

 uniniured^Mofs ^'^^ ^"°^ white and lemon yellow veins. The poIiQi of th« 

 i-aift part. ftone was not injured, but its weight was diminiflied 12 grains. 

 DifTufion of the Five hundred grains of the ignited Jlone were finely pulver- 

 powdsred ftone \2.qA, and mixed with 2000 grains of potafh, diflblved in alike 

 arti fufiin fo- quantity of water. This mixture was evaporated to drynefs 

 luti in or" the in a crucible of platina, and expofed to heat, gradually in- 

 i-adie '"uTbir' ^'^^^^^^ ^o whitenefs, for one hour. During this operation the 

 mixture fufed quietly, and exhibited when cold, a homogene- 

 ous opakemafs, of a reddifh colour. This mafs was covered 

 with water, and after having been expofed to a gentle heat, a 

 folution of it was effeded in that fluid. 

 Saturated with This alcaline folution was a little turbid, and could not be 



muriatic acid ; rendered tranfparent by repeated filtration. I faturated it with 

 gel Jtinous mafs. , . ' . ■' ' 



Dilution with muriatic acid, a white precipitate fell down, the whole.fluid 

 water. acquired a rcddiOj hue, and aflTumed a gelatinous confiflence. 



The latter could but difficultly be diminifiied, by a copious ad- 

 mixture of water. 

 Ivaporation In order to colled the precipitate which was diffufed through 



nearly to dry- j.|-,g fjujj \\-^q whole was evaporated nearly to drynefs, and thea 

 nefs, addition O' ,. , . . ■ j j ' 



dilute muriatic transferred into muriatic acid, diluted with fix times its quan- 

 acidj precipi- tity of water, and afterwards filtered. The precipitate, after 

 '•'" ' having been waflied, dried, and ignited, weighed 365 grains. 

 It was pure filex. 

 Refidun! fluid The fluid from which thefe earths had been feparated, to- 

 <onceniratcd gcther with the water expended for wathine it. I concentrated 



and faturated , . , - , . ° 



^vith carbonate ^y evaporation to about | bt its original bulk, and then fatu- 



•f potafli. rated ii with a heated folution of carbonate of potafli in excefs. 



The white precipitate which was depofited, I transferred into 



*a%I!c containing muriatic acid ; a bri{l< etfervefcence enfued, 



but no pcrtecl folution could be clfefted, by either this, cr any 



other 



