7$ Aiial\fis of the Oriental Lapis Lazuli. 



Bergmann ha\ ing prefuined that the Chinefe and Japanefe make ufe of it for the blue 

 colour of their porcelain *. To afcertain the truth, I mixed feme of the very fine powder 

 of lapis lazuli with a proper flux, and difpofed it upon porcelain, which I afterwards placed 

 in the enamcUer's furnace. My expedations were not realifed, for the colour changed to 

 a blueifli grey. 



•B. By expofure to a more violent fire the lapis was deprived of twelve centenaries of 

 •its weight, and was vitrified. I apprehend that the two parts loft by the firft ignition con- 

 fifted merely of water, and that the additional ten in the fecond eflay confifted for the nioft 

 part of carbonic acid. This opinion is fupported by the eifcrvefcence of the ftone, which 

 takes place when an acid is poured upon it, and indicates, though very feebly, that part 

 of the calcareous earth is united to carbonic acid. 



C. Upon two hundred grains of the lapis in impalpable powder I poured muriatic acid 

 diluted with an equal meafure of water (etendu de moitie eau), and digefted the whole 

 together by a progreffive heat. The colour became gradually changed to a grey afh-colour s 

 and when the ebullition commenced the powder was more ftrongly attacked, and at length 

 became converted into a thick jelly. This was diluted with water ; after which nitric acid 

 was added, and the whole boiled until the refidue had become white. The filtered folutioii 

 was of a pale yellow colour. 



D. The produft which rernained upon the filter had the appearance of fand, and weighed 

 one hundred and thirty-eight grains. When this was mixed with three parts of cauftic 

 pot-a(h, and ignited, it afforded a greenilh mafs. The folution of the mafs in water 

 •was perfeftly colourlefs. By an excefs of muriatic acid I feparated the filex, which after 

 ignition weighed 57 grains. 



E. The folutions C and D, decompofed by the carbonate of pot-afli, afforded a yellow 

 white precipitate, which, when dried, amounted to 221 grains, and was re-diflblved in the 

 muriatic acid. 



F. Ammoniac feparated from the folution E a gelatinous precipitate. This was thrown 

 -ftill wet into a cauftic lixivium, in which I digefted it. It was not totally dilTolved, but left 

 a yellowifh refidue weighing 113 grains. 



G. The fluid which remained after the precipitation by ammoniac was treated with car- 

 bonate of pot-afii, and afforded 59 grains of the carbonate of lime. 



H. Upon the 1 1 3 grains which were infoluble in the cauftic pot-afh, I poured fulphuric 

 acid diluted with water. This mixture, after having been heated, afTumed the form of a 

 jelly. It was diluted with a large quantity of water, and afforded a precipitate of filex which 

 after ignition weighed 29 grains. 



I. After the feparation of the filex I poured ammoniac into the folution. The precipitate, 

 •ftill humid, being mixed with a cauftic lixivium, depofited brown flocks in the liquor, which 

 when dry weighed 13 grains. I diffolved thefe in the muriatic acid; and this folution 

 treated with ammoniac let fall the oxide of iron, which after ignition weighed fix grains. 

 The carbonate of ammoniac likewife precipitated five grains of calcareous e.irth. 



K. The folutions f and I by tlie cauftic alkalis were treated with the muriatic "acid. The 



• Opufculej Phyfiques ct Cliymiques de Bergmann, Vol. IV. page jj. From the good quality of the cobalt 

 at prcfeni ufcd for thit purpofc in England and clfcwhcre, there is no rcafon to think that any other material is 

 ufcd for full deep blues in the Eali. N. 



precipitate 



