Intelligence and Miscellaneous Articles, 1 57 



it seemed at first to be insoluble : the solution was alkaline, and 

 was not precipitated by ammonia. It has the characteristic pro- 

 perty of becoming turbid when it is heated to about 160° Fahr. and 

 depositing a great quantity of a white precipitate, which gradually 

 redissolves as the solution cools. It is owing to the formation of 

 this salt in the mixture of solutions of sulphate of magnesia and 

 borax, that a precipitate is occasioned when it is heated. This 

 precipitation is occasioned by the formation and precipitation of 

 sub-borate of magnesia, while borate of soda and boracic acid 

 remain in solution. On evaporating the liquor separated by filtra- 

 tion from the precipitate, boracic acid evaporates with the water, 

 and a saline mass is obtained, from which alcohol separates a 

 quantity of boracic acid. This sub-borate of magnesia is most 

 readily obtained by heating a mixture of solution of borax and sul- 

 phate of magnesia. 



Hydrate or carbonate of magnesia dissolves in a hot solution of 

 boracic acid. The solution is alkaline : by evaporation it deposits 

 a salt in crystalline grains, which is very soluble in water, although 

 the solution goes on slowly. The solution is not precipitated at a 

 high temperature, but when mixed with a solution of borax, it 

 deposits a white precipitate if heated to about 160°. The preci- 

 pitate disappears at common temperatures. 



This borate of magnesia when heated to redness loses much 

 water and boracic acid. The residue has the appearance of pumice- 

 stone : water dissolves much pure boracic acid from it, and pure 

 magnesia remains. It appears, then, that at high temperatures the 

 affinity between magnesia and boracic acid is entirely destroyed. — 

 Ann. de Chim. et de Phys.> torn. liii. p. 433. 



ACTION OF TANNIN AND SOME OTHER SUBSTANCES ON THE 

 ROOTS OF PLANTS. BY M. PAYEN. 



It has been repeatedly stated by M. Silvestre, Jun., that trees 

 soon died when their roots came into contact with the remains of 

 the roots of oak trees cut down near them. This was supposed by 

 some to be owing to the action of tannin, while others maintained 

 that it was innocuous. M. Payen instituted direct experiments on 

 this subject. In order to observe the influence of tannin and to 

 appreciate its effects comparatively with those of other agents, 

 M. Payen placed grains of wheat, rye, barley, oats, and maize, in 

 contact with equal quantities of the following liquids, and all other 

 circumstances were equal: 1st, aerated distilled water; 2nd, the 

 same containing 0-01 of its weight of a saturated solution of car- 

 bonate of soda; 3rd, the same containing only 001 of its weight 

 of the same saturated solution of carbonate of soda; 4th, a solution 

 containing 0*001 of pure tannin ; 5th, a solution containing 0*001 

 of sulphuric acid ; 6th, distilled water saturated with lime. 



In the distilled water, in the liquid containing 0*001 of solution 

 of carbonate of soda, and in the solution of tannin, germination took 

 place in the order stated ; in the three other liquids, those contain- 

 ing 0001 of acid, 0*001 of carbonate of soda, and saturated with 

 lime, germination did not occur. 



