602 CONSIDERATION OF CARBON COMPOUNDS. 



volatile alkaloids are precipitated from the acid solution by 

 the addition of an alkali, and the impure alkaloid thus obtained is 

 purified by again dissolving in an acid and reprecipitating, or by dis- 

 solving in alcohol and evaporating the solution. 



As the quantity of alkaloids in plants, and consequently in the aqueous 

 extract made from them, is often so small that the precipitation process gives 

 unsatisfactory results, a second method known as the shaking-out process is often 

 employed for the separation of alkaloids. In using this process the con- 

 centrated aqueous extract, to which a suitable alkaline precipitant has been 

 added, is agitated with a liquid (such as chloroform) not miscible with water 

 and acting as a solvent upon the alkaloids. The operation is performed in an 

 apparatus known as separator or separatory funnel, consisting of a globular or 

 cylindrical glass vessel, provided with a well-fitting stopper and an outlet-tube 

 containing a glass stopcock. Having introduced into this vessel the extract 

 and solvent, the latter is made to dissolve the alkaloids present by a rapid 

 rotation of the separator. As the aqueous solution and the solvent do not mix, 

 but form two distinct layers one above the other, they may be conveniently 

 separated by opening the stopcock until the heavier liquid has run out. By 

 evaporation of the liquid, used as a solvent, the alkaloids may be obtained in a 

 more or less pure condition. 



Assay methods. As the medicinal value of many drugs, such as opium, 

 cinchona bark, etc., as also that of the galenical preparations, such as tinctures, 

 extracts, etc., obtained from such drugs, depends chiefly on the alkaloids pres- 

 ent, and as the quantity of the alkaloids in drugs varies considerably, the 

 U. S. P. gives specific assay methods for the estimation of the percentage of the 

 alkaloids contained in drugs or in certain preparations. 



These assay methods must be closely followed by the analyst, as otherwise 

 results may be obtained which are either too high or too low. This is due to 

 the fact that these methods in many cases do not give absolutely correct results, 

 but give results sufficiently accurate for all practical purposes, provided the 

 directions of the Pharmacopeia are closely followed. To bring about a 

 standard and uniformity in alkaloidal strength is the object of these assay 

 methods. 



Antidotes. In cases of poisoning by alkaloids the stomach-pump and emetics 

 (zinc sulphate) should be applied as soon as possible ; astringent liquids may be 

 given, because tannic acid forms insoluble compounds with most of the alkaloids. 

 In some cases special physiological antidotes are known, and should be used. 



Detection of alkaloids in cases of poisoning 1 . The separation 

 and detection of poisonous alkaloids in organic matter (food, contents 

 of stomach, etc.), especially when present in very small quantities, as 

 is generally the case, is one of the most difficult tasks of the toxi- 

 cologist, and none but an expert who has made himself thoroughly 

 familiar with the methods of discovering minute quantities of organic 

 poisons in the animal system should undertake to make such an 



