On the Decompo/itlon tf the Acid of. Borax. 263 



ing the refiduum with water, it yielded fixty-eight grains of fait, and there" were not quite 

 two grains left upon the filter. 



Exper. 'KXWWL On treating thefe fixty-eight grains of fait in the fame manner, they 

 yielded a few drops of fluid, and two grains of fublimate; after filtration, there remained 

 forty-eight grains of fait, and a refiduum of hardly one grain and a half. ' 



Exper. XXIX. The fame fait, treated in the fame manner, yielded a few di^ps and a little 

 fublimate; and after filtration thirty-five grains of fait and a refiduum of hardly one grain. 



Exper. XXK. On treating thefe thirty-five grains of fait in the fame way, they yielded, 

 befides a very fmall quantity of fluid and of fublimate, twenty-four grains of fait, and about 

 three quarters of a grain of refiduum. 



As I now difcovered that the quantity of fait was continually decreafing, and fome coal fe- 

 parating from it, I thought it fuperfluaus to endeavour to decompofe the above twenty-four 

 grains any farther. 



Exper. XXXI. The refiduum /3 of exper. XXII. was light, blackift, and like coal. I 

 now poured common concentrated muriatic acid upon three grains of it, and digefted the 

 mixture for forty-two hours in a confiderable degree of heat, but no diflTolution was apparent. 

 I then^dded fmoking nitrous acid, and digefted it for twenty-four hours, till ij' boiled with- 

 out any apparent diflLlution. I added fome fugar (about two grains), but without eiFeft, 

 except that its colour grew yellowifli. I now boiled the fluid till it all evaporated in reddifh- 

 yellow vapours ; there remained a very black, thick, glutinous mafs, fmelling like burnt 

 fugar. Having added three ounces of water, the greateft part of the blackifli matter rofe to 

 the furface, and the water appeared only a little tinged : the fluid part, indeed, became brown 

 by boiling, but after reft and fubfidence, it again grew clear. I filtered it a ; then poured 

 two ounces more diftilled water upon the refiduum, and after digefting, boiling, and filtering, 

 added the filtered fluid b to the former a. After this treatment there remained two grains of 

 refiduum c. 



Exper. XXXII. Having caufed the fluid a i of exper. XXXI. to evaporate, it yielded a 

 fait greyilh yellow mafs, which very quickly attra£ted the moifture of the air. Being again 

 difTolved in water, and faturated with potafli, a confiderable quantity of whitifli earth was 

 precipitated very much refembling talc. 



Exper. XXXIII. The refiduum c of exper. XXXI. which, befides its infolubility and 

 lightnefs, had much of the external appearance of coal, was now thrown upon melted nitre, 

 and it deflagrated. I placed a fecond crucible with melted nitre clofe to it, and after having 

 at the fame moment thrown into one the abovementioned refiduum, and into the other a 

 quantity of common charcoal pulverifed, I could not obferve the fmalleft difference in effeft. 

 Very little difi^erence was alfo apparent as to the refiduum /3 of exper. XXII. c of exper. XXIV. 

 and that of the following experiments. 



(To be continued.) 



VII. 



