262 On the Decompofttion of the Acid of Borax. 



(bumber of the whiteft cryftals (hot forth from the black ground, forming fmall groups ; 

 but the retort was cracked. 



Exper. XXI. I therefore took all the veffels afunder, and fHooIf the retort well, till what- 

 ever hung upon its fides was difTolved ; then diftilled the fluid in another retort, till the mafs 

 of fait appeared quite dry. I now put the retort into a crucible, furrounded it with fand, 

 titted another receiver to it, and placed the crucible in an open fire. Firft fome fublimate 

 was produced towards the neck of the retort, (but which vanifhed as the heat increafed), and 

 then a fmall portion of fluid (hardly more than a dram, or a dram and a half), which appeared 

 tofmell a little of the febacic acid. At the bottom of the retort was a blackifli mafs a, and 

 Jikewife fome fublimate b-, which by its varied appearance feemed to be of a two-fold nature. 



Exper. XXII. The refidilum taken out of the broken retort had a fpongy appearance, 

 and fwam upon water. It had a blackifh colour, and weighed three drams and ten grains. 

 Being expofed to the air, the blackifh colour became lighter, and inclining to grey. When 

 digefted in fixteen parts of diftilled water in the ufual temperature for two days and a half, 

 it did not at all fink to the bottom ; and after being digefted with heat for twenty hours, it 

 was not entirely difTolved : that part which funk was of a blackifh-brown. More water was 

 then added, and it was made to boil for two hours ; it was afterwards placed upon a paper 

 filter (the weight of which was previoufly afcertained), and edulcorated with boiling diftilled 

 water, till at laft a proportion of twenty-fix parts of water to the fubftance had been ufed. 

 After all the fluid a. hadpafi'ed through, and the filter with the refiduum had been dried in a 

 heat of 212° for an hour and a half, the refiduum /S weighed, exclufive of the filter, nine- 

 teen grains. 



Exper. XXIII. The fluid « obtained by exper. XXI. was fufFered to evaporate gradually, 

 and yielded three drams and ten grains of a white tranfparent fait. 



Exper. XXIV. This fait (obtained by exper. XXIIl.) was put into a fmall retort, and 

 expofed in a crucible filled with fand to an open fire. It became of a blackifh brown colour, 

 yielded fome fublimate a (about five grains), a fmall portion of fluid b, and a blackifh brown 

 refiduum c, which grew lighter in colour on being expofed to the air. 



Exper. XXV. The fluid b (of exper. XXIV.) fmelt like marine acid, and precipitated 

 nitrate of lead. 



Exper. XXVI. The refiduum c (of exper. XXIV.), by the addition of fome water, be- 

 came whiter, and was difTolved ; more water having been added, it was digefted with heat, 

 by which the matter was difTolved. The folution being afterv/ards filtered, I obtained two 

 drams and four grains of white fait : the refiduum upon the filter weighed four grains. 



Exper. XXVII. Ttiis fait (exper. XXVI.) I again expofed to the fire, when it yielded 

 from twenty to thirty drops of acid liquor, four grams of fjblimate, and a refiduum, which 

 being difTolved, yielded one dram and thirty -three grains of fait, and left two grains and a half 

 c upon the filter. 



The fame fait (obtained by exper. XXVI.) being diftilled, became of a brownifh-grey 

 colour,. and befides a few drops of fluid yielded not quite two grains of fublimate. On heat- 

 ing 



