80 ORGANIC CONSTITUENTS. 



Capi'yllic acid, at the ordinary temperature, forms a smeary 

 mags ; below 50" it crystallizes in needles, wliicli are of difficult 

 solution in water, have an acid and acrid taste, and a peculiar 

 disagreeable odour. The baryta salt separates from hot solu- 

 tions in brilliant laminse, but on spontaneous evaporation in 

 white granules. It is anhydrous^ is not affected by exposure 

 to the air, does not fuse at 212°, and is very sparingly soluble 

 in water. 



Capric acid resembles caprjdlic acid in its properties. The 

 baryta salt crystallizes from hot solutions in minute fatty 

 needles and scales, and on spontaneous evaporation likewise in 

 scales, arranged in dendritic groups ; it is very difficult of 

 solution, is anhydrous, and is not affected by exposure to 

 the air. 



Vaccinic acid. Vaccinate of baryta separates in nests of 

 crystals, which have already been described ; they contain 

 water of crystallization, effloresce very readily in the air, 

 become very similar in appearance to chalk, and diffuse a 

 strong odour of butter, while pure caproate and butyrate of 

 baryta do not effloresce in the least, and have scarcely any 

 odour. Vaccinate of barji;a is soluble in water to alaout the 

 same extent as butyrate of baryta; the saturated solution is 

 thick like oil. When vaccinate of baryta is dissolved in 

 water, and again evaporated in a retort, it crystallizes from the 

 solution unaltered; but if the crystals are exposed for some 

 time to the air, they at last lose nearly all their odour, and 

 no longer when dissolved crystallize on evaporation, but in 

 their stead crops of caproate and butyrate of baryta are ob- 

 tained. The same happens when a solution is exposed to the 

 air for any length of time, or boiled in an open dish. No 

 baryta separates in this change, no acid vapours are given off, 

 and the solution remains perfectly neutral. Vaccinic acid 

 therefore saturates exactly the same amount of barj^ta as the 

 two acids which have originated from it ; the relative quantity 

 of the caproate and but}a-ate of baryta formed is proportionate 

 to the atomic weights of these two salts. If vaccinate of 

 baryta is decomposed by sulphuric acid, with free access of air, 

 and the separated acid removed by distillation, saturated with 

 baryta, and set aside to crystallize, a mixture of caproate and 

 biatyrate of baryta only is obtained. On adding some solution 



