236 J. L. Smith on determining the Alkalies in Minerals. 
9. The following extract from Rose’s Analytical Chemistry, 
(translation by Normandy, in a note by the translator,) presents 
fairly the difficulties casnendlite this method of docontpatngaas 
silicates : 
“The heat applied is so intense, that some precautions must be ta- 
ken. The platinum setae containing the mixture should be exposed 
first to the heat of an argand-lamp, and when the mass begins to agglu- 
tinate, the crucible iootd be closed, and its cover tied down with pla- 
tinum wire, then placed in a Hessian crucible, closed up also; the 
whole is placed upon an inverted crucible, and submitted to the action 
of the blast of a wind furnace, aegis ing first gradually with a red 
heat, piling on more coke, so as o fil up the furnace, and increasing 
the heat to the highest possible bitch. until the Hessian crucible begins 
to soften. It is absolutely necessary to the success of the gacborye 
that the Hessian crucible should be closed as well as possible, which is 
best done by luting the cover with fire-clay ; the Hessian crucible vid 
its epee having fused together, cannot be separated, except by 
ing, &c. 
It will be seen in reading this extract, that the heat requivellt 1s 
not ordinarily at the command of most chemists, in fact no other 
variety of furnace ed a Sefstroem can be depended on for a 
complete decomposit 
austic lime aiid its salts ra also been recommended and 
long used for the more imperfec t decomposition of 1 ae 
carbonate well mixed with many silicates finely pulverized er 
decompose them completely at a white heat, but no one 
lime is capable of meeting the demand of the entire range © ‘tk 
kaline silicates. 
11. In consideration of these difficulties, Berzait proposed 
the use AG hydro-fluoric acid, and this method w en applied with 
the numerous precautions required, will serve 3 “decot 
most all dienes still, according to Rose, there are silicious con 
pounds that cannot be completely decomposed by hydro-fluoric 
acid. Besides, this acid is a most disagreeable one to manipula 
with, whether we employ Brunner’s apparatus, or Laurent’s meth- 
od, or what is always the best, the concentrated acid, For! 
prepare . I may also add, that the necessity of using sulph a 
acid, after the decomposition is made, is another “pbjectionab 
feature i in this process. we 
- The above furnishes a hasty review of the methods 
are now possessed of for decomposing the poten in order 
determine their alkalies; their merits can be c trasted W wih 
those a bi taethod about to be described. 
13. substitute 
he decomposing agent which I present as @ 
for all oth and as bapabie of meeting ‘the tere a em sed 
in the commencement of this article, 1 is a micture © 
lime and fluor spar. 
