Technical Chemistry. 269 
eyanid, aie a reddish- Aap liquid which gradually becomes darker 
and finally appears carmin 
This reaction is obtained with molybdie acid or solutions of molyb- 
dates by putting a fragment of zinc into the liquid, adding a few drops 
of strong solution of sulpho-cyanid of potassium, and, finally, a little 
sulphuric or chlorhydrie acid, so that a gentle evolution of hydrogen is 
excited. The red wie shortly pings —— it is not permanen 
In this way, syy'5a0 Of molybdic acid is recognizable, a quantity less 
than can be detected by the usual tesende The sulpho-cyanid of mo- 
with it. It is not dissolved by chloroform or sulphid of carbon. 
Since ferric oxyd and hyponitric acid give with alkali-sulpho-cyanids 
red liquids, they interfere with the direct detection of molybdenum. 
C. Clau s has observed that — ue ea itebia: acids i the 
to aren the Rivet acid, then treated with phasor, pe and 
~ iy with zinc and sulpho- eyanid of potassium. w. J. 
- On the ene estimation of Arsenic. — Wirrsrers (Zeitschrift 
hg te Chemie, 1863, 19) observes that the process of drying the 
et of magnesia in vacuo is extremely tedious, while at 
100° C, of ammonia may occur. He recommends to expel all the 
water pene ammonia and weigh the pyro-arseniate of magnesia. To do 
this, it is necessary to heat the substance cautiously and gently in a sand- 
bath, until atree ammonia is expelled and the original snow- white color 
has to milk-white. Then the heat is gradually increased u ntil the 
porcelain cbutible almost glows. The residue is 2MgO AsO,, and no loss 
of arsenic is to be feared, except through too-rapid heating. . 8. Ww. J. 
Trcaxicat Cueistey. . 
ll. On =a ‘manufacture of Soda, Chlorine, and Sulphuric and Chlor- 
hydric Acids; by Tuomas Macrartaye.—lIn the Canadian Naturalist 
for Sebursiey, 1863, Mr. Macfarlane has described a series 
admixture of nt of i sie which renders the mass 
~ fasible and keeps it ina porous state. 828 parts of green vitriol are 
dried and partially peroxydized by a gentle seit and are then intimately 
