194 Miscellaneous Intelligence. 



it has a cool, bitter taste. It dissolves in 2J parts of water, at 55 

 F., whilst gallic acid requires 100 parts at the same temperature. 

 When re-sublimed, pyrogallic acid is decomposed almost entirely, 

 producing tannin and charcoal. It dissolves in ether. Its aqueous 

 solution is colourless, but by exposure to air becomes coloured, and 

 deposits ulmin, being entirely decomposed in a few days if water be 

 added as evaporation proceeds. Persulphate of iron added to it is 

 immediately reduced to protosulphate, and a tanning matter is 

 formed. Protosulphate of iron produces a blue-black liquor. These 

 actions are very different from those of gallic acid, which with proto- 

 salts of iron produce no change, and with persalts produce a fine 

 blue colour. 



Pyrogallic fccid slightly heated with strong sulphuric acid does 

 not become coloured, and is not sensibly decomposed. Pure gallic 

 acid treated in a similar way became coloured, but on adding water 

 was found not much altered ; no tannin was produced. Strong sul- 

 phuric acid and a higher temperature converted the gallic acid into 

 ulmin ; no tannin was formed. 



Pyrogallate of alumina forms a bitter solution, becoming turbid 

 by heat, and transparent when cold ; it powerfully coagulates gela- 

 tine ; crystallizes ; and reddens litmus paper more powerfujly than 

 the acid alone ; as if alumine itself acted as an acid. 



Every endeavour to form gallic acid (upon Berzelius' views), by 

 combining pyrogallic acid and tannin, failed. From all these facts, 

 M. Braconnot concludes, i. That gallic acid procured in the humid 

 way, and cleansed by animal charcoal, is pure ; ii. That heat con- 

 verts it into tannin and pyrogallic acid ; iii. That gallic acid cannot 

 be produced from tannin and pyrogallic acid *. 



21. SuLPHO-SlNAPISINE, OR SULPHO-SlNAPIC ACID. 



MM. Henry and Garot described some years since a curious product 

 derived from white mustard-seed (sinapis alba), which they called 

 sulpho-sinapic acid, to point out at once its source, the presence 

 of sulphur in it, and its acid nature. Some discussion has arisen 

 relative to the subject, M. Pelouze having denied the existence of 

 this acid, and referred the properties observed to the presence 

 of sulpho-cyanic acid or its compounds. This has drawn forth 

 a memoir from the discoverers and from others, in which many 

 curious points relative to this body are established. We do not in- 

 tend to enter into the controversy, but wish to give an account of the 

 points really established, or, at least, most recently ascertained. The 

 following account is from MM. Henry and Garot's second memoir. 



Sulpho-sinapisine is prepared by boiling the coarse powder of 

 white mustard-seed, or of the turrites glabra, for a minute, with 

 five or six times its weight of distilled water, in a copper vessel, the 

 liquid passed through a cloth, and the solid portion pressed. The 

 magma, when exposed to the air, evolves a sulphurous smell. The 



* Annales de Chimie, xlvi., 206. 



