10 



The fact that every aqueous extract of vegetables reddens the 

 litmus-paper shows, that the akaloids are not present in the free 

 state in the organism, but bound to acids as salts. Generally, these 

 salts dissolve readuy in water, except the tannates, which dissolve 

 slowly or not at all. In the latter case, i.e., when tannic acid is 

 present, the extraction, in. order to be exhaustive, has to be carried 

 on by means of a very diluted mineral acid (100 parts water to 

 about two parts of sulphuric or hydrochloric acids). Alkalies and 

 alkaline earths decompose all these salts easily by combining with 

 the acid and leaving the alkaloid free, whereby the latter, accord- 

 ing to its nature, is either volatilised or remains in the solution or 

 is precijiitated. By these characteristics is also indicated the way 

 for obtaining the alkaloids in general. 



The volatile alkaloids are at ordinary temperature liquid, colour- 

 less, of a strong specific odour of the plant used for their prepara- 

 tion, mostly heavier than water (of those which are known, only 

 coniin is lighter than water), of alkaline reaction, readily soluble 

 in water, alcohol, ether and acids. 



The non-volatile alkaloids are mostly white, seldom yellow, 

 without odour, mostly of an eminently bitter or acrid taste, of 

 amorphous or crystalline structure, heavier than water, fusible or 

 not, slowly or not at all soluble in water, but readily so in acids 

 and mostly in alcohol too, and partly in ether, of feeble alkaline 

 reaction even in the saturated alcoholic solution, 



Alkanua-red = Anchusin. 



Alchoniillt Peculiar substance, obtained from the bark of 

 Alchornea latifolia by extracting with alcohol, treating the exti'act 

 with ether, and evaporating the ethereous solution. White, pointed 

 crystals ; readily soluble in alcohol, ether and oil of turpentine, 

 but not in alkalies and diluted acids. Its existence has been re- 

 peatedly questioned. 



Aloill = C34 His Oi4+ HO. In the aloes (the dried juice of 

 the leaves of various species of the genus Aloe). In some sorts of 

 aloes it exists in the amorphous form, and can therefore not be ob- 

 tained pure. Best adapted for its isolation is the Barbadoes aloe. 

 Extract with cold water, evaporate in vacuo to a syrup, leave to 

 cool, collect the separated crystalline grains, press and recrystallise 

 in water of not more than 65°. It appears in sulphur-yellow gi-ains 

 when crystallised in water, and in concentrically radiated needles 

 when crystallised in alcohol, of at first sweetish, afterwards intensely 

 bitter taste, without odour and of neutral reaction. It loses the 

 water on the waterbath, and when left there for a longer time it 

 loses more water and becomes partly converted into a brown, amor- 

 phous resin. Afterwards it fuses and decomposes gi-adually. Dis- 

 solves in 600 parts of cold water, readily in alcohol, ether and 



