ON FLUOR 51 



p. 397.) That this subject might not remain in obscurity for want of 

 investigation, Mr. Wenzel of Dresden likewise made a number of 

 experiments on fluor, which coincide in every essential point with those 

 of Mr. Meyer, though they differ in a few particulars. The title of his 

 pamphlet is, G. Wenzel's Chymische Untersuchung des Fluss-spaths. 

 Dresden bey Gerlach. 1783. 4to. 



Mr. Wenzel, in order to obtain the fluor acid free from siliceous earth 

 performed the distillation in a leaden retort provided with a glass 

 receiver ; there appeared, however, upon the water in the receiver a 

 variegated crust, and the acid, with fixed alkali, yielded a gelatinous 

 precipitate. Upon examining the receiver, he found that the vapours had 

 corroded its internal surface, so that it appeared as if it had been rubbed 

 with coarse sand. Mr. Wenzel, however, accomplished his purpose, by 

 substituting a balloon of lead in the place of a glass receiver, and by 

 distilling with a gentle heat. At the end of the operation, there was no 

 appearance of any earthy crust, either in the retort or on the surface of 

 the water in the receiver : the acid liquor gave no jelly on the addi- 

 tion of alkali, though there was a precipitation of iron and earth of 

 alum. 



To complete his proof of the origin of the siliceous earth, he mixed 

 fluor, quartz, and vitriolic acid, and performed the distillation in hi 

 apparatus of lead. But he now found the usual crust upon the acid 

 liquor, and obtained a gelatinous precipitate on the addition of alkali. 



Moreover, Mr. Wenzel observed that 2 oz. of fluor lost upon calcina- 

 tion in open vessels only 2 grs. When this experiment was performed 

 in an air apparatus, some inflammable air was obtained, and a very small 

 quantity of fluor acid, which attacked the glass. Fixed alkali threw 

 down a precipitate, amounting, after proper edulcoration, to 1 oz. 22 grs., 

 from the acid expelled by oil of vitriol from 2 oz. of fluor. This pre- 

 cipitate was very fusible, and yielded fluor acid with oil of vitriol. 

 Both fire alone and vitriolic acid expelled a little acid of fluor from the 

 earthy crust. When the precipitation from the same quantity of acid 

 was made by volatile alkali, 2 drms. and 53 grs. of an infusible substance 

 were obtained, which likewise, on addition of vitriolic acid, yielded 

 some fluor acid. It appears, then, that a portion of it is contained in the 

 earthy crust, and that even fixed alkali is not capable pf separating it 

 completely from siliceous earth, but it remains united with some 

 siliceous earth and alkali after precipitation. 



The residuum, after distillation, contains calcareous and aluminous 

 earth ; this at least was the case with the German species examined by 

 Mr. Wenzel, 



