ALOE. 



687 



half its weight of aloes, forming an acid liquid which exhibits similar 

 reactions. The solution of aloes in potash or ammonia is precipitated 

 by acids, but not by water. 



The most interesting constituents of aloes are the substances known 



o _ ...... 



as Alo'in, This name was originally applied to an aloin which, as it 

 appears to be found exclusively in Barbados aloes, is now termed^ Bar- 

 hdoin, in order to distinguish it from allied substances occurring in 

 Natal and Socotrine aloes. 



Barbalom was discovered by T. and H. Smith of Edinburgh in 1851,' 

 and was described (1851) by Stenhouse. From good qualities of the 

 chug it can be obtained, according to Tilden,^ as a crystalline mass, to 

 the extent of 20 to 25 per cent., but in others it appears to occur partly 

 amorphous or in a cbemically altered state. Barbalom is a neutral sub- 

 stance, crystallizing in tufts of small yellow prisms. These crystals 

 represent hydrated aloin, and part with one molecule of water (= 2G9 

 per cent.) by desiccation in vacuo, or by the prolonged heat of a water- 

 bath. Barbaloin, C''H'"0'' + H-Q, dissolves sparingly in water or alcohol 

 hut very freely if either liquid be even slightly warmed ; it is msolubie 

 in ether. 



The solutions alter quickly if made a little alkaline, but if neutral 

 or slightly acid, are by no means very prone to decomposition. By 

 oxidation with nitric acid, barbaloin yields, as Tilden (1872) has shown, 

 about a third of its weight of chrysammic acid, besides aloetic, oxalic, 

 and picric acids. It easily combines with bromine to form yellow 

 needles ofBromalom, C'^^ff «Br«0^^ CUoralom, G'^WVi 0" + GH-0, cry- 

 stallizing in prisms, has likewise been obtained. , . , 



In examining Natal aloes in 1871, we observed it to contam a 

 distinct nrv«fflli;T.n ^.^r^.r .^..r^h 1p«« Roluble than the ordinary aloin ot 



We have accordingly 



aloin. 



Nataloin exists naturally in Natal aloes, from which it can be eas 1} 

 prepared in the crude state, if the drug is triturated with an equ. 

 ^eight of alcohol at a temperature not exceeding 48 U -^^^^ ^^m 

 dissolve the amorphous portion, from which the crystals «I'0"^^ t.e 

 separated by a filter, and washed with a small quantity ot coM s^^^^^^^^ 

 From IG to 25 per cent, of crude nataloin in pale yellow crystals ma> be 

 thus extracted. \Vhen purified by crystallization from ^^thyhc a^^^^^^^^ 

 or spirit of wine, it forms thin, brittle, rectangular ^P'-^^^^' f^^^^ .^^^ 

 or more of their angles truncated. The formula f fj^"^^^ ,^°/Xrh Lu ve 

 Tilden, which is supported by the composition of the acetyl demative 



he has succeeded in obtaining, is a'H-^0". , ,. , v^i 3 xn nf acetic 

 ^ At 15-5° C, 60 parts of afcohol, 35 of methylic alcohol fjl^^l^^ 

 ether, 1236 of ;ther, and 230 of absolute alcohol, dissolve respectnel^ 

 one part of nataloin. It is scarcely more soluble m ^^arm ^^^^^^^ 

 spirit of wine, so that to obtain crptals it is best to allow the solution 

 to evaporate spontaneously. Water hot or cold ^^^^f \^ 

 sparingly. Nataloin gives off no water when exposed ovei oil ol ^ 1 1 ol , 



or to a temperature of 100° C. By the action^ of »V^^^%^"^^' ^^f ;,t 

 hoth oxalic and picric acids, but no chrysammic acid. It appeals 



J]lft beautiful specin,ens have been pre- f The best crystals eau be got by this 



2 m ^'^ *^^^^^ o^ ^^s by these gentlemen. solvent. 



i'hani. Journ. April 28, 1872. 845, 

 5>ee also Nov. 5, 1870 375. 



