482 Dr. Stenhouse on Aloine, the Cathartic Principle 



the solubility of the aloine is exceedingly increased : the 

 colour of these solutions is pale yellow. Aloine is also very 

 readily dissolved by the carbonated and caustic fixed alkalies 

 in the cold, forming a deep orange-yellow solution, which 

 rapidly grows darker, owing to the oxidation which ensues. 

 The effects of ammonia and its carbonate are precisely similar. 

 When aloine is boiled either with alkalies or strong acids, it 

 is rapidly changed into dark brown resins. A solution of 

 bleaching-powder likewise gives aloine a deep orange colour, 

 which soon changes to dark brown. Aloine produces no 

 precipitate in solutions either of corrosive sublimate, nitrate of 

 silver, or neutral acetate of lead. It also yields no precipitate 

 with a dilute solution of subacetate of lead ; but in a concen- 

 trated solution it throws down a deep yellow precipitate, which 

 is pretty soluble in cold water, and is therefore difficult to 

 wash. This precipitate is by no means very stable ; and when 

 it is exposed even for a short time to the air, it becomes brown. 



When powdered aloine is thrown, in small quantities at a 

 time, into cold fuming nitric acid, it dissolves without evolving 

 any nitrous fumes, and forms a brownish-red solution. On 

 adding a large quantity of sulphuric acid, a yellow precipitate 

 falls, which, when it is washed with water to remove all ad- 

 hering acid and then dried, explodes when it is heated. It 

 plainly, therefore, contains combined nitric acid. I could not, 

 however, succeed in obtaining this compound in a crystalline 

 state, as when it was dissolved in spirits, it appeared to be 

 decomposed. When aloine is digested for some time with 

 strong nitric acid, much nitrous gas is evolved, and it is con- 

 verted into chrysammic acid, but without the formation of any 

 nitropicric acid, as is always the case when crude aloes is sub- 

 jected to a similar treatment. A quantity of aloine was boiled 

 with a mixture of chlorate of potash and muriatic acid. The 

 acid solution was evaporated to dryness, and digested with 

 strong spirits of wine. The greater portion of the spirits was 

 removed by distillation ; and the remainder, when left to spon- 

 taneous evaporation, yielded a syrup which could not be made 

 to crystallize. Not a trace of chloranil was produced. 



When aloine is destructively distilled, it yields a volatile oil 

 of a somewhat aromatic odour, and also a good deal of resinous 

 matter. When aloine is heated on platinum foil it melts, and 

 then catches fire, burning with a bright yellow flame, and 

 emitting much smoke. It leaves a somewhat difficultly com- 

 bustible charcoal, which, when strongly heated, entirely dis- 

 appears, not a trace of ashes being left. 



A quantity of aloine dried in vacuo was analysed with chro- 

 mate of lead in the usual way. 



