28a New Publication. 



they contain will diflblve the acid, and the filex will he pre* 

 cipitated upon them. 



If this experiment be made in a metal veffel, the fame in- 

 cruftation will not take place. 



It thence refults that the earthy fubftance which is pre- 

 cipitated by the contact of the fluoric acid gas and the water, 

 is nothing elfe than a portion of the glafs, which is attacked 

 and aftually diflblved by the aeriform acid. 



It often happens alio, that when this gas is made to pafs 

 into water, the filex is precipitated in a qnartzy pellicle. 

 Each bubble of the acid which touches the water is imme- 

 diately enveloped in filex, and leaves on its way as it afcends 

 to the furface of the water, traces in the form of tubes, 

 which Prieftley calls organ-fifes, and which decreafe to a 

 point upwards, becaufe the bubble dccreafes in proportion as 

 the water diflblves it, and the filex is thus carried off. 



The filex depofited in the veflels is foon after re-difiblved 

 by the excefs of acid, in proportion as the water is faturated ; 

 for the water, being at firft little faturated with the acid, has 

 not fufficient ftrength to hold the filex in folution. 



Bergman obtained filiate of filex in a cryftallized form. 



When the fluor'iG acid is made in earthen veffels, you wil} 

 have filex depofited, and then re-diflblved by the re-aclion 

 of the acid : this is a real fluate of filex inftead of pure flu, 

 oric acid. 



Alkalies may be employe! for detecting the prefence of the 

 filex. The tafte of this acid, diflblved in water, is like that 

 of the fulphuric acid diluted with water, or of vinegar. 



If a folution of fluoric acid in water be expofed to heat, 

 part of the acid is volatilized ; but the laft moleculae adhere 

 fo ftrongly, that the water and the reft of the acid are vo- 

 latilized, if the heat be increafed. 



This acid is preferved in bottles covered on the inflde with 

 wax diflblved in oil, or in vefl'els of lead or of platina. 



Guyton employed this property to engrave labels on bot- 

 tles, and in particular on thofe deftined to hold acids, the 

 -labels of which when made of paper are always burnt. 



The elements, of this acid are ftill entirely unknown. - 

 [To be continued.] 



INTEL, 



