458 Chronicles of Science. [ July, 
Next comes the discovery of thallium in the Nauheim spring, in 
which cesium and rubidium also exist. Professor Bottger* an- 
nounces that thallium is present in the saline residue of the water in 
an appreciable quantity; but Werther, who has also examined the 
residue, states that he was able to obtain but a mere trace in 4 pounds. 
Professor Schrétter, of Vienna, announces that he has also found thal- 
lium in lepidolite and mica. There can be no doubt that this metal 
is widely diffused in nature ; but the means occasionally employed to 
separate 1t sometimes suggests that the thallium may have been con- 
veyed to the substance in “the reagents made use of. Béttger supposes 
that thallium always exists in pyrites in the form of thallium-iron 
alum, a salt, the composition, properties, and crystalline form of which 
have been recently determined by Messrs. Church and Crookes, and 
Professor Miller, of Cambridge.t The existence of thisalum is held 
to support the hypothesis that thallium belongs to the series of alka- 
line metals; but by the same reasoning, silver may also be proved to 
be an alkaline metal, since Professor Church has recently $ made 
known the existence of a silver alum. 
That the field of inorganic chemistry so far from being exhausted, 
is still capable of yielding rich results, has been once again proved by 
M. Marignac, || who has discovered a remarkable series of silico- 
tungstic acids, and described their compounds. We need notice but 
one of these bodies, most noteworthy from the extraordinary density of 
the solution it gives with water. Stlico-tungstic acid is formed when 
gelatinous silica is boiled with an acid tungstate of soda or potash. 
It is composed of one equivalent of silica and 12 equivalents of tung- 
stic acid, and is a very stable compound, forming hydrates, which can 
be obtained in crystals of large size. When in combination with soda 
the salt gives an aqueous solution, having the specific gravity of 3:05 ; 
in this solution, glass, quartz, and most stones will float. The solu- 
tion, notwithstanding its great density, is very fluid, and it has been 
suggested ¥ that it may form an excellent material for use in fluid 
prisms. 
M. Kuhlmann has fallen upon some curious results in the course 
of investigations he has been led to make on the preservation of 
materials for building and ornamental purposes. 
Some of these results are as important to geologists and mineralo- 
gists as to chemists, particularly those on the production of pseudo- 
morphic crystals. By passing sulphuretted hydrogen over crystals of 
carbonate of lead kept at a moderate temperature, M. Kulhmann found 
that the carbonic acid in the compound was completely replaced by 
sulphur, while the crystal retained its original shape. Malachite 
treated in a similar way became converted into sulphide of copper, 
* «Proceedings of Manchester Literary and Philosophical Society, March 22 ; 
and ‘ Journal fiir praktische Chemie, No. 6, 1864, 
+ ‘Journal fiir praktische Chemie, No, 7. 1864. 
t ‘Chemical News, vol. ix. p. 205. 
§ ‘Chemical News,’ vol. ix. p. 155. 
|| ‘Comptes Rendus, May 2. 
4 «Chemical News,’ vol. ix. p. 238. 
