240 
POPULAE SCIENCE EEYIEW. 
texture. Eventually, however, the contraction increases, and then the 
resultant is a homogeneous substance, having a gummy aspect, and which 
splits up into a white compound like sugar, but of a sour character, and con- 
taining besides other materials glucose and a new acid.^^ If the writer had 
given himself the trouble to consult the Journal of the Chemical Society 
before announcing his grand discovery, he would have found that he had 
been anticipated. In a paper read before the Chemical Society in 1863, 
Dr. Divers distinctly demonstrated the nature of the phenomenon observed 
when gun-cotton is exposed to light, by showing that this substance under- 
goes decomposition into jpectic and parorpectic acids. In Yol. III. p. 108 
of this Eeview, the reader will find an abstract of Professor Divers’s memoir 
to which we have alluded. 
How to prepare Aluminium. — A. very questionable process for the 
preparation of this metal has been described by a M. Corbelli. The clay 
from which the metal is to be obtained is first cleansed from stones, bits of 
wood, and other accidental impurities, and dried. One hundred grammes 
are then washed in nitric, sulphuric, or hydrochloric acid, in order to remove 
the iron which is usually present. The purified clay is next dried and heated 
in a crucible to 450° or 500° centigrade, and then 200 grammes of prussiate 
of potash are ‘thrown in, and the whole is heated to whiteness. The button 
of pure aluminium is then found in the bottom of the crucible. 
The Alcohols of Thallium. — M. Lamy, who claims (unjustly) to be the 
discoverer of the metal Thallium, has presented an exceedingly interesting 
memoir upon the above subject to the French Academy. The first compoimd 
which this chemist succeeded in obtaining was with a member of the Ethyl 
series, and to it he then gave the name of Thallic alcohol. Since discover- 
ing this he has studied it more carefully, and found it to be not only heavier 
than all known liquid compounds, but to possess greater dispersive and 
refractive powers also. In the hope of obtaining a liquid of a still more re- 
markable character as regards optical properties, he was led to examine a 
homologous compound, in which one of the Amyl series took the part of the 
Ethylic portion of the first, and found its properties not so extraordinary as 
those of the Ethyl compound. Finally, he was enabled to prepare a Methyl 
compound. The three combinations are termed respectively Ethyl-thallic 
alcohol, Amyl-thallic alcohol, and Methyl-thallic alcohol. Of these the two 
first are liquid at ordinary temperatures, and the last is solid. The first is 
the heaviest and (optically) most refractive and dispersive compound with 
which chemists are famihar. It crystallizes at about 3° below zero, and is 
prepared as follows : — Place a large excess of absolute alcohol in a large flat- 
bottomed vessel under the receiver of an air-pump, and place on a wire 
gauze above the liquid a number of thin plates of Thallium. Exhaust 
the air in the receiver, and put the latter in communication with a bag of 
oxygen by means of tubes, some of which are filled with sulphmic acid and 
pumice, and others with potash at 20° or 25° centigrade : the Thallium is 
rapidly transformed into a heavy oil, which falls through the alcohol to the 
bottom of the vessel. In this way, says M. Lamy, a hundred grammes of 
heavy oil may be easily produced in twenty-four hours. Amyl-thallic 
alcohol may be prepared in a somewhat similar manner, but with less 
rapidity ; whdst the Methyl compound is produced in a granulated white 
