214 Miscellaneous Intelligence. 



bonic acid and azote were evolved during their decomposition by 

 heat. 



Oil the Bitter Principle from Aloes. — Upon distilling 8 parts of 

 nitric acid from 1 part of the extract of aloes, and adding water to 

 the remaining fluid, a resinous reddish yellow substance precipi- 

 tated, which, by washing, became pulverulent — it was discovered 

 by M. Braconnot. Upon evaporating the liquid separated from the 

 precipitate, it gave large yellow rhomboidal crystals, not transpa- 

 rent, and but slightly soluble. These crystals, at first mistaken for 

 a particular substance, were soon found to be a combination of 

 oxalic acid with the bitter of aloes. The bitter substances of aloes 

 dissolved in 800 parts of water, at 59° F., but in a smaller quantity 

 of boiling water. This solution has a superb purple colour. Silk 

 boiled in it acquired a very fine purple colour, on which neither 

 soap nor acids effected any change, except nitric acid ; this changed 

 the colour to yellow, but it was restored simply by washing in water. 

 All shades may be given to this colour by proper mordants. Wool 

 is dyed black in a peculiarly beautiful manner, by the same process, 

 and light has no influence on the colour. Leather acquires a pur- 

 ple colour; cotton, a rose colour; but the latter will not resist soap. 

 Dr. Liebeg thinks that this is the only substance from which a perma- 

 nent rose dye for silk may be expected. — Ann. de Chimie, xxxv. 72. 



25. On the Existence of Crystals of Oxalate of Lime in Plants.— ^ 

 M. Raspail has read a memoir to the Academy of Sciences, to prove 

 the analogy which exists in arrangement between the crystals of 

 silica, which are found in sponges, and those of oxalate of lime oc- 

 curring in the tissue of phanerogamous plants. 



The latter crystals were observed, for the first time, by Rafn and 

 Jurine, who regarded them as organs of which they knew not the 

 use. They were then observed by M. de Candolle, who called 

 them raphideSy and gave a figure of them, which, however, is inac- 

 curate. These crystals are really very regular tetraedrons. In 

 many plants, as orchis^ pandanus, ornithogahim, jacinthus, phy- 

 tolaca decandria, mesembryanthemum deltoides, &c. they are very 

 small, not being more than -g^^ of a millimetre ( . 0002 of an inch) in 

 width, and ^^y ( . 004 of an inch) in length. But, in the tubercles of 

 the Florence iris, they are as much as 3^^ ( . 0008 of an inch) in 

 width, and ^ (.01312 of an inch) in length, so as to be easily ca- 

 pable of examination. — Bull. Univ. B. xi. 376. 



26. Fallacy of Infusion of Litmus as a Test, by M. Magnus. — 

 When pure water is heated for a sufficient time with infusion of 

 litmus, reddened by an acid, it restores the blue colour. It is sup- 

 posed that the heat gradually causes the free sulphuric acid, which 

 had occasioned the reddening, to combine with the excess of alkali 

 contained in the infusion, and thus to cause the restoration of the 

 blue colour. Hence this preparation cannot be used to test the 



