390 
POPULAR SCIENCE REVIEW. 
that the metal itself does not exist in the sun. This is a fact of great 
importance, not only in regard to ordinary chemistry, hut as it bears on 
toxicology. For in an analysis (spectral) of the animal tissues or liquids, 
•one is certain to find chloride of sodium in abundance, and therefore, 
were thallium present in small proportions, it would escape detection by 
this method. If it be required to examine mineral waters and such-like 
for thallium, it will be necessary to separate the metal in the first instance 
from the excess of soda ; this may be done by one of the methods pointed 
out by M. Lamy ; viz., either by depositing it on zinc, or reducing it by 
galvanic means, or by precipitating it with sulphide of ammonium or 
iodide of potassium. — See a memoir by M. Nickles in the Comptes Rendas 
for January, 1864. 
Soap for very Dirty Hands. — The following is a novel German receipt for 
the manufacture of a soap whose cleansing properties are said to be of a high 
order : — Two pounds of finely rubbed carbonate of magnesia are to be 
mixed in a porcelain dish, with eight pounds of waterglass and eight 
pounds of water. To these, four pounds of oleic acid are added, and 
the whole is gently warmed and stirred as long as carbonic acid is evolved. 
Lastly, a pound of crystallized carbonate of soda dissolved in some warm 
water is added, and the mass is dried, and made into shapes. — Vide Chemical 
News , January 3rd, 1864, and Chemisches Centralblatt , No. liv., 1863. 
Non-existence of Tyro and Meta-Arseniates. — The currently received 
opinion that the phosphates and arseniates are analogous compounds has 
been refuted by M. Maumene. In a memoir laid before the French 
Academy in the beginning of February last, he asserts most positively that 
neither of the compounds above referred to has any real existence. It 
was thought by Pelouze that the arseniates, like the phosphates, were 
modified by heat and converted into salts having other proportions of 
base and acid. M. Maumene states that “ it is nothing of the kind ; 
arseniate of soda never gives either pyso-arseniate or meta-arseniate. 
Submitted to an intense heat violently or carefully, or for a lengthened 
period, it does not undergo the slightest alteration of the sort imagined. 
Dissolved in water, and then mixed with a silver solution it invariably 
gives the brick-red arseniate As, 0 5 , 3, Ag, O. Arseniate of soda was kept 
at a red heat for several days, and its properties remained unaltered, and 
when added to solution of nitrate of silver the brick-red arseniate was 
produced ; a similar result was obtained by employing the acetate instead 
of the nitrate of silver. Arseniate of potash was obtained from acid pre- 
pared by Gay-Lussac’s method, and heated to redness with the same 
results as when the soda salt was experimented on. Finally, M. Maumene 
treated the arseniates of baryta and lead in a similar manner, and pro- 
duced a silver-precipitate like that which the soda salt gave rise to, thus 
affording conclusive proof of his assertion that the modified arseniates do 
not really exist. 
The Decomposition of Iodide of Mercury. — This may readily be effected 
by employing the cyanide of potassium. In order to estimate the pro- 
portion of mercury in the iodide the following method may be employed. 
The evanide of potassium is first rubbed down in a mortar, with twice its 
weight of quicklime. Then a tube, closed at one end, is taken, and a small 
