53 



Experiments on the fixed alcali through which the red fumes were made to pass 

 in the second process for making neut. arsen. salt. 



P. 8. The contents of the vessel after distillation were found to weigh 19*7'0 ; 

 so that the f. alk. appears, instead of increasing in weight, to have lost about 

 13 parts by the operation : these contents were put in a bottle, & set in 

 sand, in order to dissolve the sediment which, as was before said, fell to the 

 bottom during the process : the bottle broke, but the liquor was saved by the 

 sand-pot ; it was washed out from the sand by boiling it with fresh parcels of 

 water; it weighed 36'0*0 : into some of this liquor was dropt oil of vitr. 

 diluted with about 3 times its weight of water ; it effei-vesced, & discharged 

 a great quantity of red fumes like those produced in the distillation, & turned 

 of a blue colour : the same phenom. were produced also by spt of nitre & 

 spt of salt : distilled vinegar made an efFerv., but did not discharge any fumes ; 

 nor did the liquor turn blue, but of a pale madeira colour. 



It appears from hence, that the nitrous acid is so much altered by this 

 process as to have a less affinity to f. alk. than the marine acid, though not 

 so small, I suppose, as distilled vinegar. 



Experiments on the solutions of arsenic in the mineral acids — of the arsenical 

 acid — 8f conjectures concerning its nature. 



P. 9. l-O-O of arsen. was put into a flor. flask with 2-0-0 of oil of vitr. With 

 the assistance of a heat almost enough to make the oil vitr. boil, it dissolved, 

 but without the least efferv. On cooling, there formed an irregular crystallized 

 mass at bottom, which weighed about I'lO-O ; some of this crystallized mass 

 was put into an open cylindrical glass & held over the fire : after some of 

 the moisture had boiled away it dissolved into a transparent glass : after 

 standing some time, it grew opake, & attracted the moisture of the air enough 

 to swell, & burst the glass, but not enough to deliquiate or grow moist. It 

 appears from hence, that arsen. united to the concentrated acid of vitr. bears 

 a much greater heat than either of the 2 substances separate : the same thing 

 is observed of turbeth mineral. 



19'4 of arsen. was put into a flor. flask with 2" 17-4 of strong spt of salt & 

 about 4 part as much water ; it made no efFerv. during heating ; but by the time 

 the liquor began to boil, it was found to be entirely dissolved : on cooling, a 

 good deal of white matter stuck to the sides, & some small crystals shot. 



If some f. alk. is dropt into this solution, it effervesces, & instantly pre- 

 cipitates the arsen. in white clouds. 



P. 10. The phenom. attending the solution of arsen. in aqua fortis were 

 found to be very different ; for whereas arsen. dissolves very readily in the 

 vitr. & marine acids with the assistance of a sufficient heat, but without the 

 least efFerv. : on the contrary, it dissolved very slowly in the nitrous acid, but 

 made a great efFerv., & discharged a great quantity of red fumes resembling 

 those produced in the distillation of neut. arsen. salt, & the solution became 

 of a bluish-green ; whereas the solut. of arsen. in the vitr. & marine acids did 

 not in the least incline to that colour : moreover the arsen. by being dissolved 

 in this acid was found to have undergone the change necessary to enable it to 

 form the neut. arsen. salt when united to f. alk. : for no arsen. was precip. 



d2 



