Chemistry and Physics. 405 
d 
vantageous in the preparation of aluminum to mix the finely pulverized 
mixture, 8 or 10 grammes of sodium are to be used. The crucible must 
be previously strongly dried. It is then to be quickly heated to a white 
heat in a good furna At the moment of reduction a noise is heard 
and some sodium is volatilized which burns with flame. r this the 
heat must be kept up for a quarter of an hour to fuse the mass com- 
8. Researches on the Fluorids—Fremy has communicated the results 
5s 6 ’ . . 
(1.) Fluohydrie acid may be obtained from anhydrous acid in a state 
of purity by calcining, in a platinum apparatus, the fluohydrate of fluorid 
of potassium, previously dried. In this state the acid is gaseous at ordinary 
d salts. es 
i i lity; the 
(4.) The anhydrous fluorids are remarkable for their stability; 
h i table, and sometimes decompose 
ydrated fluorids are, on the somite “< e Be Goyaiio 28. aml 
eaving as a residue an oxyfluorid or oxyd. ru 
(4) The Grueids so Steel tendency to unite to form double fluorids ; 
is prc belongs even to the insoluble fluorids. Thus these last 
compounds must never be prepared by double decomposition, — 
they always retain, in their state of double salt, a part of the soluble 
salt which has bee Joyed in their preparation. : 
(6.) Hydrogen rye Tob devott/poee all the fluorids “ the aid of heat ; 
. Md i 
ori : . 
gr ili ‘dg of lead, tin, &e. ‘The reduction of the metal- 
he fuoride = SL caeageerttia Bate of lead and tin, which resist the action 
