Chemistry. 369 
17. Test-Paper for Acids, Alkalies, and Compound Salts . — 
A useful test-paper has been submitted to the Society of Arts 
of London, by Mr Thomas Griffiths. Acids change the blue 
colour of the test-paper into red, and alkalies change it into 
green. It is thus prepared. A pound of the minced leaves of 
red cabbage, are boiled in a pint of distilled water, till all the 
blue colour is extracted. The liquor is then strained through 
a cloth or sieve, and the clear infusion, which is of a fine blue 
colour, is to be evaporated to half its bulk, and poured into a 
shallow dish. The paper may then be dipped into it, and hung 
on lines to dry. A sheet of the filtering paper, which is the kind 
used, absorbs two fluid ounces of the infusion. With this test- 
paper, only one drop of the solution to be boiled is required. 
There are, no doubt, several processes, in which a test for acid 
and alkali at hne operation may be found advantageous. See 
the Transactions of the Society of Arts for vol. xli. p. 78. 
18. Mineral Waters. — M. Berzelius has found in mineral 
waters, many substances which have not hitherto been observed 
in them, mz,jiuate (flime, carbonate (fstrontian, phosphate of' 
lime, and phosphate of alumina. These substances are found in 
the waters of Carlsbad, dissolved in carbonic acid uncombined. 
The tufas deposited by these waters are arragonitic, which con- 
firms the idea of M. Stromeyer, that it is the carbonate of Stron- 
tian which determines the arragonitic form of the species of car- 
bonate of lime. — Professor Silliman’s American Journal, vol. vii. 
p. 185. 
19. Reduction (f Uranium. — M, Arfwedson has found, that 
uranium is very reducible by means of hydrogen gas, at a tem- 
perature scarcely equal to redness. The combination of the 
yellow oxide of uranium, with barytes, lead and iron, are redu- 
cible in the same way, and give metallic uranures, which take 
fire when they come in contact with air, and burn like pyro- 
phori. — Professor Silliman’s American Journal, vol. vii. p. 185. 
20. On the Corrosion of the Coppering (f Ships.— At a 
meeting of the Royal Society on the 22d January, Sir Humphry 
Davy read a paper on the cause of the decay and corrosion of the 
coppering of shipSj which he ascribed to a constant though feeble 
chemical action of the saline parts on the surface of the copper. 
