107 



HydrOCarotilirrCse H30 O2. Besides carotin in tlie culti- 

 vated root of Dauciis Carota. The alcoholic solution of hydro- 

 carotin and mamiit. obtained in the preparation of Carotin, throws 

 down on cooling a red brown mucilaginous deposit, and forms, 

 after the latter has been removed and the liquid allowed to rest for 

 eight days, crystals, consisting of Hydrocarotin and mannit. 

 Remove the mannit by dissolving in water, and purify the H. by 

 recrystallising several times in the least possible quantity of boil- 

 ing alcohol, and lastly by boiling with water. — Forms colourless, 

 large, flexible, rhombic lamellae, without taste or smell; floats on 

 water like a fat, without being wetted; becomes at 100° hard and 

 bi-ittle, a little above 100° yellowish and soft, then dark yellow ;^ 

 fuses at 126° without loss of weight, and consolidates again resin- 

 like; is destroyed by a higher temperature; is insoluble in water, 

 soluble in boiling alcohol and crystallising almost entirely on 

 cooling; readily soluble in ether, sulphide of carbon, chloroform, 

 benzol, oils, in concentrated sulphuiic acid, with vividly red 

 colour, and thrown down by water in the amorphous state ; not 

 soluble in alkalies. 



Hydroelateriii. See Ecbolin. 



Hydrocyanic Aci(l=HC2 N or HCy., does probably not exist 

 as such in the living vegetable organism, but appears always, 

 when amygdalin {see " Amygdalin") is decomposed under access of 

 water. It is easily detected by its odour of bitter almonds, or by 

 distilling the substance in question with water, adding to the 

 distillate potash-ley in suflicient quantity to blue litmus-pai^er, 

 then a stale solution of subsulphate of iron, and after agitation 

 hydrochloric acid in excess, when a deep blue precipitate or a 

 similar colouration will indicate the presence of Hydrocyanic acid. 

 [Very minute traces of H. acid are, according to Almen, detected 

 by adding to the colourless distillate one drop each of diluted 

 soda-ley and of hydrosulphide of ammonium, evaporating the 

 whole, on the water-bath, acidifying with 1-2 drops of hydrochloric 

 acid, and adding a little chloride of iron. A more or less blood- 

 x'ed colouration ensues through the formation of sulphocyanide of 

 iron.] 



Quantitatively the amount of Hydrocyanic acid is determined 

 by mixing, the distillate or a certain fraction of it, with nitrate of 

 silver, then with ammonia in excess, and after agitation with 

 excess of nitric acid. The precipitate is collected, washed and 

 dried at 100°. After noting down its weight, it is heated in 

 a porcelain crucible, until reduced to the metallic state. The 

 remaining silver is dissolved in nitric acid, and any insoluble 

 portion (chloride of silver), filtered ofi", washed, dried at 100°, and 

 its weight deducted from that of the first precipitate. The i"est 

 gives the weight of the \)\xve cyanide of silver, which, divided by 



