and Attached Water. 



109 



§ 248. Pyrogallate of Aniline*. — 3*7270 grams of the solu- 

 tion saturated at 17° # 8 yielded 1*7440 gram dry salt in vacuo, 

 or 46*80 per cent. Of a solution saturated at 0° 0., 5*92 grams 

 gave 1*992 gram of the dry salt, or 33*65 per cent. As a 

 cryogen the temperature — 4°*6 was obtained, and the cryo- 

 hydrate showed the same temperature. 9*397 of cryohydrate 

 gave 2*253 of salt, or 23*98 per cent. The above results, and 

 the separation of solid matter on loss of heat, are exhibited in 

 the following table : — 



Table LV. 



Pei* cent, of 

 pyrogallate 

 of aniline 

 by weight. 



Per cent, of 



water 

 by weight. 



Temperature 



at which 



solidification 



begins. 



Nature of 

 solid. 



9-09 

 20-00 

 2398 

 33-65 

 46-00 



90-91 

 80 00 

 7602 

 66-35 

 5100 



- f-0 



- 27 



- 4-6 ' 

 



4-17-8 



Ice. 



Cryohydrate. 

 1 Salt. 



The curve corresponding to these numbers is found in 

 fio\ 2. It is to be noted that amongst all the curves referring 

 to the aniline salts, that belonging to the nitrate alone has a 

 well-marked concavity on its ascending branch (from the 

 cryohydrate to the right) turned towards the axis of strength. 

 The very important signification of this curvature will form 

 the key "to much in the next Chapter referring to the limit of 

 solubility, or rather to the unlimited solubility in certain cases 

 of certain salts, especially nitrates. 



* As I do not find any account of this body, I may briefly note its pre- 

 paration and properties. On mixing the two substances pyrogallic acid 

 and aniline, a dry hard mass is obtained. As this is soluble in aniline, 

 only a slight excess of the latter is used. The solid mass is dissolved in a 

 minimum of hot benzol ; cooled to about 5°, filtered, and washed with cold 

 benzol. Amongst its properties are the following : — It fuses at 126° C. 

 or 128° 0. It is very soluble in water, hot and cold • also in hot and cold 

 alcohol and ether ; soluble in hot benzol, very sparingly in cold ; very 

 sparingly soluble in bisulphide of carbon, hot or cold. Fused on glass, it 

 forms a beautiful crystalline film, the crystals being several inches long. 

 It is anhydrous. In another preparation, 1 part of pyrogallic acid was 

 dissolved in 4 parts of water at 50°. Aniline was added until a specimen 

 became cloudy on cooling. It was cooled to about 10° and filtered through 

 wet paper. It was then evaporated to about half its bulk and dried in 

 vacuo over sulphuric acid. It turns brown on exposure to the air. 



