304 Scientific Notices — Chemistry. [Oct. 



Article XVII. 



SCIENTIFIC NOTICES. 



Chemistry. 



1 . Ignition supported bij Hydrophosphoric Gas, S;c. (Extract of 

 a Letter from M. J. B. VonMons to M. Planche.) 

 I have lately observed, on kindling phosphuretted hydrogen 

 not spontaneously inflammable, that the bubbles which are 

 slowly generated maintain the ignition of a lighted match, with- 

 out inflaming it, and are themselves inflamed by the incandes- 

 cent flameless body : this has some relation to Doebereiner's 

 lamp. You have undoubtedly already seen that hydrogen, after 

 having burnt for some minutes in the philosophical candle, heats 

 the end of the tube sufficiently to cause the gas to be relighted 

 immediately after it is blown out. The hydrogen in this candle 

 inflames spontaneously if the mixture of the sulphuric acid and 

 the water be made in the bottle itself.— (Journal de Pharmacie.) 



2. Effect of Prussic Acid on Vegetation. 

 C.I.Th. Becker (Dissertatio de Acidi llydrocyanici Vi perni- 

 ciosd in Plant as. Jena, 1823. 4to.) has made many experi- 

 ments, from which it follows that prussic acid prepared by 

 Vauquelin's method destroys vegetables nearly in the same 

 manner as it acts on animals. Seeds steeped in this acid either 

 die or lose the power of germinating. The more delicate vege- 

 tables perish under its influence sooner than the more robust. — 

 (Journal de Pharmacie.) 



3. To preserve the Colour of Red Cabbage. 

 Digest the leaves of the cabbage in warm alcohol, and when 

 the whole of the colouring matter is extracted distil off a por- 

 tion of the spirit, and evaporate the remainder, at a very gentle 

 heat, to the consistence of a syrup. This extract may be pre- 

 served unimpaired for years, if kept in closely stopped phials. 

 In order to use it, it is only necessary to add a small portion of 

 it to water, in which it is readily soluble, when the addition of 

 an acid or an alkali will produce its peculiar effect. When we 

 wish to employ this test to discover small quantities of carbonic 

 acid, it is necessary to render it slightly green by the addition of 

 a diluted alkali. The carbonic acid will then restore the blue 

 colour, by saturating the alkali. Test papers may also be pre- 

 pared by means of the alcoholic tincture of the cabbage, which, 

 when rendered green by immersion in a diluted alkaline solution, 

 may be used in all those cases in which litmus papers are com- 

 monly employed. — (American Journal of Science.) 



