90 SCIENCE: 
CURRENT NOTES ON CHEMISTRY.—V1I. 
(Ldited by Charles Platt, PhD., F.C.S.) 
SILICON CARBIDE. 
CarsIbDE of silicon, or ‘‘ carborundum,’” has already be- 
come a familiar term, andthe material is now upon the 
market as a formidable competitor of the highest grade 
abrasives. It is interesting to note some of the chemical 
aspects of this substance as given by Dr. O. Miihlheeuser. 
To obtain the pure compound corresponding to the 
formula SiC the crystals are heated to dull redness in 
oxygen, boiled with potash solution, washed, digested 
with hydrochloric acid, again washed, and finally treated 
with hydrofluoric and sulphuric acids. It is insoluble in 
all acids, but is attacked by molten alkalis and by hot 
ferric oxide and, when very finely divided, can be slowly 
burned in oxygen. Its specific gravity is given as 3.22 at 
15 C, but the fine powder will remain suspended in water 
for months. The following suggestions are made for 
analysis: The powder obtained by trituration in an agate 
mortar is submitted to elutriation and the carbon deter- 
mination made with that portion which remains in sus- 
pension after five minutes. The carbon is best estimated 
by combustion with twenty parts of lead chromate, the ad- 
dition of potassium dichromate causing the oxidation to 
proceed with explosive violence. The silicon is deter- 
mined by fusion with potassium sodium carbonate for about 
six hours, during which time the heat should be increased 
very gradually. A very pure specimen gave by analysis: 
-Carbon, 30.2 per cent; silicon, 69.1 per cent; oxides of 
iron and ealumina, 0.46 per cent; lime, 0.15 per cent; 
magnesia, 0.09 per cent. 
H. Moissan has produced the carbide by dissolving car- 
bon in fused silicon, but states that it can be much more 
easily prepared by heating in an electric furnace a mixture 
of twelve parts of carbon with twenty-eight parts of silicon. 
It is also produced by heating carbon and sv/ica in the 
electric furnace or by allowing the vapors of carbon to 
come into contact with vapor of silicon, when it is obtained 
in almost colorless, very hard and brittle, prismatic 
needles. Moissan gives the specific gravity at 3.12, which 
is also that determined by Professor J. W. Richards. 
According to Moissan, the carbide is not affected by 
oxygen at 1000°C, nor when heated in air by a Schloesing’s 
blowpipe. Sulphur vapor at rooo® is also without action, 
while chlorine attacks the compound very slowly at 600° 
and rapidly at 1200°. Fused potassium nitrate, or chlorate, 
boiling sulphuric acid, nitric acid, and hydrochloric, aqua 
regia, and mixtures of nitric and hydrofluoric acid are all 
without action. Fused lead chromate oxidizes the carbide, 
but repeated treatment is necessary to obtain complete 
combustion. Fused potassium hydroxide gradually con- 
verts it into potassium carbonate and silicate. Muiihlhzeuser 
has also described a boron carbide obtained by heating a 
mixture of boric anhydride with carbon in the electric 
furnace. A graphite-like mass is obtained, which after 
further heating in a platinum crucible and boiling with 
acids yields, on analysis, BC, or B,C,. It is described as 
a black powder having similar properties to graphite, burn- 
ing with difficulty in oxygen, insoluble in nearly all of the 
usual solvents and decomposed by fusion with alkali. It 
is significant that the Carborundum Company are about to 
increase their capital stock, and that among other recent 
orders one has come from London calling for $10,000 
worth of material. 
FORMATION OF PRECIOUS OPAL BY THE ACTION OF 
HYDROFLUOSILICIC ACID ON GLASS. 
Proressor G. Cesiro, of the University of Liége, de- 
scribes in the Bulletine of L’Académie Royale de Belgique 
the formation of precious opal and other substances by the 
action of hydrofluosilicic acid on a glass-containing vessel. 
IW, R, Blake in Sczence, XXII., 554, p. 141. 
Vol. XXIII. No. 576 
The glass was attacked very unequally, the upper portion, 
that above the level of the liquid, being acted upon most 
strongly, with the production of cellular cavities contain- 
ing a white translucent substance. In these cavities and 
also attached to the bottom of the flask were likewise 
found beautiful, limpid crystals of hexagonal form with 
others, unattached, which were apparently tetragonal. 
The opalescent mass was built up of concentric layers, 
which were easily separated and which produced fine 
iridescent effects. This substance proved to have the 
composition, silica, 90 per cent; water, 10 per cent; 
corresponding precisely to the precious opal of Hungary 
and from the chemical point of view to the polysilicic 
acid, 3 SiO,. H,O. ‘The formation of this opal is easily 
understood from the reaction: 
6 Si0,. Na,O. CaO-+-2 H, Sif =Na, Sif, 
Ca Sif 2 (3 Si0,. H,O) 
The hexagonal crystals found by their chemical and 
physical properties were determined as _ fluosilicate- of 
sodium, Na, SiF,. The crystals give in converged light a 
uniaxial interference figure; they are negative in character 
and show a weak double refraction. The index of re- 
fraction for the ordinary ray is 1.300 and for the extra- 
ordinary ray 1.296. ‘The remaining crystals, spoken of as 
apparently tetragonal, were determined to be biaxial and 
orthorhombic ("= 4/3), consisting of a soluble potassium 
fluosilicate. Finally in the liquid was found a fluosilicate 
of calcium. It will be seen that both the fluosilicate of 
calcium and of sodium, as wellas the opal itself, are ex- 
plained in the reaction above given. 
These experiments recall the historic ones of Daubrée 
in Paris, who, by superheated water alone, altered a glass- 
containing tube with the production of hydrated silicates 
resembling zeolites (Pectolite?) and of an alkaline silicate 
in solution,together with innumerable colorless, bipyramid- 
al crystals of quartz, minute spherulites, microlites and 
even a green pyroxene (Diopside?). 
INERTNESS OF QUICKLIME. 
Ir is now a well-known fact that in the absence of 
moisture many elements and compounds which ordinarily 
react upon each other readily and even with explosive 
rapidity are rendered inert. ‘Thus mixtures of oxygen 
and hydrogen if perfectly dry can not. be exploded by the 
electric spark. Many chemists are now working on these 
lines, and all contributions are of interest in extending the 
experimental data. Mr. V. H. Veley has already shown 
in the Journal of the Chemical Society of London that 
quicklime does not combine to an appreciable degree with 
carbonic or sulphurous acids at temperatures below 300°C., 
and now in a more recent paper he has investigated the 
reaction between the same substance and chlorine. ‘The. 
result of Mr. Veley’s experiments is to confirm the 
observation of others, his conclusions being, first, that dry 
chlorine does not combine with dry lime at ordinary tem- 
peratures to form the so-called bleaching powder; 
second, that no appreciable chemical change is obsery- 
able between these two substances below a temperature of 
300°, when a partial replacement of oxygen by chlorine 
takes place, the conditions being analogous to that of 
baryta and chlorine not specially dried and at ordinary 
temperatures. It seems probable to the writer that 
Veley’s method of ‘‘drying ” is the real explanation of the 
slight reactions obtained below 300°, in other words that 
no action would take place below that temperature were 
the chlorine and lime aésolutely dry. 
BARIUM AND STRONTIUM IN SILICATE ROCKS. 
Ara recent meeting of the Geological Society of Wash- 
ington, and later at the Baltimore Meeting of the Ameri- 
can Chemical Society, Mr. W. F. Hillebrand presented a 
