170 Intelligence and Miscellaneous Articles. 



usually aggregated in a very peculiar manner ; it is very sparingly 

 soluble, has a very distinct acid taste, resembling that of bitartrate 

 of potash. When exposed to heat the crystals lose water, and be- 

 come opake without efflorescing. At different temperatures it ap- 

 pears to lose portions of the water which it contains, and under cer- 

 tain circumstances, which have not been altogether determined, it 

 appears to crystallize wth a different quantity of water than that 

 alluded to ; in all cases, however, it loses all its water at 212°, with- 

 out decomposing. 



Euchroic acid appears to be composed of 



2 equiv. Hydrogen. . 12*479 

 12 Carbon 917-022 



4 Oxygen .. 400000 



4 Azote 354-008 



Equivalent 1683-509 

 In its crystallized state it contains 10-67 per cent, of water. 



Euchroic acid may be heated to 536° Fahr. without alteration ; if 

 the temperature be higher than this, it fuses, boils up and decom- 

 poses into cyanide of ammonia, and a deep green and extremely bitter 

 sublimate. The aqueous solution undergoes no change by boiling, 

 even when hydrochloric or nitric acid is added ; but if the acid be 

 heated to 212° in a close tube with less water than is sufficient to 

 dissolve it, it is then decomposed and converted into mellitate of 

 ammonia, and dissolves without precipitating on cooling. 



Euchroic acid is distinguished from all known organic acids by its 

 action on metallic zinc ; it is converted into a deep blue substance 

 which precipitates upon the zinc undissolved by the acid. The co- 

 lour is so deep, that the smallest traces of the acid are discoverable 

 by it, when a drop is put on bright zinc : this blue substance does 

 not quit the zinc when boiled in the solution of the acid, but the 

 blue deposit becomes almost black, with a reddish tint like indigo. 

 If the zinc be immersed for a second in dilute hydrochloric acid, 

 the blue body dissolves and may be separated by the filter ; when 

 washed and dried, it is a black substance containing no zinc ; when 

 slightly heated, it gradually becomes white, and is reconverted into 

 euchroic acid ; it acts exactly like the colourless indigo of Ber- 

 zelius, except conversely with respect to colouration. This property 

 of euchroic acid resembles a reduction, and the blue substance may 

 be considered either as a lower degree of oxidation or as the radical 

 of the acid ; if the latter opinion be adopted, M. Wcehler proposes 

 to call it euchrone. 



When this substance is dissolved in ammonia or potash, the solu- 

 tions have a beautiful purple colour, exceeding in this respect and 

 also in intensity those of oximanganate of potash and murexide ; but 

 no sooner do the solutions come into contact with the air, than they 

 bcin to decolorize at the surface, and by agitation they become 

 perfectly colourless. 



Euchrone is deposited upon platina when it is galvanically com- 

 bined with zinc and immersed in a solution of the acid ; the proto- 



