178 «=F. W. Clarke on a new process in Mineral Analysis, 
Fluorid of sodium is subject to neither of these disadvanta- 
ges, and in the mixture with bisulphate of potassa, has slight 
ereeninees as regards rapidity of action. 
It may not be out of place for me to mention here a fact 
ahi with eg use of Huorid of ammonium for decomposing 
silicates, as described by Rose. After fusing the mineral with 
the fluorid, he directs treatment with sulphuric acid, for the 
purpose of converting the bases into sulphates. find that if, 
in the first place, sulphate of ammonia is mixed in excess with 
the fluorid, all the bases are directly converted into pa ars 
snensry obviating the necessity of treatment with sulphuri 
“This mathod can be used for the purpose of determining ‘ 
kalies in silicates, but is far inferior to J. Lawrence Smith 
rocess. 
Technical determination of ‘chromium in chromite —Atter 
fusion with cryolite and bisulphate of potash as previously di- 
rected, the mass is to be treated with a little strong pee! | 
acid, and allowed to digest for about ten minutes. Then, upon 
boiling, with water, the whole dissolves. The solution should 
then be neu utralized, acetate of soda added, and the chromium 
oxydized to chromic acid by a current ofschlorine gas, or by 
boiling with hypochlorite of soda solution. The chromium 
may then be separated from other substances as directed in 
Prot. Gibbs’s paper in this Journal for Jan., 1865. When chro- 
mite is fused with bisulphate of potash and cryolite, and salt- 
petre is added to the mass, as soon as clear fusion is ob 
the chromium is nearly all oxydized to chromic acid. If the 
mass be boiled with a solution of carbonate of soda and the 
liquid filtered, a filtrate is obtained which contains nearly all, 
but not quite ‘all the chromium as alkaline chromates, free: om 
iron or alumina; but, invariably, the residue upon the filter 
contains traces of chromium. When chromite is fused with 
the acid fluorid of potassium, a part of the chromium is usually 
oxydized to chromic acid by the oxygen of the air; and in one 
ease that came under my observation, when I came to heat the 
resulting mass with sulphuric acid, red fumes were given off, 
ace were probably the so-called terfluorid of chromium. 
echnical estimation of iron in ores, slags, and cinders.— 
in fusion with eryolite and bisulphate of potash, the mode 
of treatment varies according to the method it is desired to 
use for determinati tion of the iron. If Penny’s process of esti- 
