216 NITROGEN BODIES OF MODERN CHEMISTRY. 



oldest of the nitrogen compounds, the all prevailnig bitter, picric acid. 

 This substance is of a pale-3'ellow color; by day a ber.utiful yellow, at 

 night white. Picric acid dyes animal fabrics yellow, without the use of a 

 mordant-; it is almost poisonous, and particularlj' hostile to insects. It is 

 proved by experience that animal fabrics impregnated with picric acid, 

 with vrhich we must iiiways accept the yellow tint, are never attacked 

 by moths or insects of any kind. When it is admissible, viz., when the 

 color is not an objection and there is question merely of the preservation 

 of the material, the use of picric acid may be warmly recommended. It 

 is not so poisonous as to involve any danger in its use. Picric acid may 

 be fixed in vegetable fabrics when these are impregnated with a solu- 

 tion of caseine in borax. Still the acid can never be made perfectly fast 

 in these textures, while for animal fabrics it furnishes one of the most 

 durable of yellow dyes. This acid was formerly obtained from different 

 substances — from indigo, for exami)le. Common Bengal indigo, evap- 

 orated Vv'ith nitric acid, leaves a deposit, which on the application of 

 heat decrepitates feebl3^ This is picric acid. 



Aloes, which is unfortunately in so common use as a drastic purga- 

 tive, digested with nitric acid also yields picric acid. 



Eecently the most abundant source of picric acid is gum acaroid, from 

 an Australian tree, {Xantliroehoca hastilis.) This resin, acted on by nitric 

 acid, affords the highest percentage of picric acid. I must mention one 

 more substance ; and this is obtained by the action of nitrogen from gly- 

 cerine, the so-called oleo-saccharum, a vfidely-difi'ased article, v.'hich has 

 the formiilii : 



C3 H5 H3 O3 



Yv^e may suppose it a three-fold water, in which three atoms of hydro- 

 gen are replaced by the bivalent radical glyceryl, 



C Hs 

 We can substitute nitryl for three atoms of the hydrogen in the 

 glycerine and then we have triuitroglycerine, glonom, or glonoidin, the 

 Swedish explosive oil, a body first produced and examined by Sobrcro, 

 and which is heavier than water, (l.OS.) To prepare this we add a de- 

 ciliter of the purest glycerine, free from water, to Nordhausen sulphuric 

 acid and red fuming nitric acid, mixed in the proportions of 0:4; 

 thus, c. g.j one liter to 600 cubic centimeters and 400 cubic centimeters, 

 which mixture must be kept ice-cold ; it should stand in the cold several 

 hours. Then this liter is poured into at least ten liters of ice-cold water, 

 and the heavy, colorless oil, triuitroglycerine, sinks to the bottom ; it 

 should be well washed in water, in which it is nearly insoluble. In watery 

 alcohol it dissolves v.itli dif&culty, but readily in absolute alcohol, etlier, 

 and pyroxylic spirit. It has a sweet but unpleasant taste, and induces 

 protracted headache, so that the homoBopathists have seized upon it as 

 a specific against headache. This Swedish explosive oil is apparently 

 the most formidable of the nitrogen bodies ; while one gram of gun- 



