178 ALKALOIDS. 



water, and is possibly an oxyaloin. Bromine does not appear to 

 precipitate it from aqueous solutions. 



170. Carthamin, etc. Some substances, more freely soluble in 

 alcohol than in ether, and characterized by their yellow colour, 

 have been already mentioned in 152, in connection with 

 quercitrin (rutin, robinin, luteolin, etc.), and whilst referring to them 

 here, I will also allude to carthamin, the colouring matter of 

 safflower. 1 It has been obtained in the form of an amorphous 

 powder, of an orange-green colour and metallic lustre. It is 

 sparingly dissolved by water, but easily by aqueous alkalies and 

 alcohol; from alkaline solution it is precipitated by acids. It 

 dissolves in ether, and stains silk rose- or cherry-red. 



ALKALOIDS. 



171. Colour-reactions. The following reagents may be recom- 

 mended for producing colour-reactions with alkaloids : Pure 

 sulphuric acid ; sulphuric acid, containing a little nitric acid (1 in 

 200); sulphuric acid, containing O'Ol gram of molybdate of soda 

 in each cc. (Frohde's reagent) ; sulphuric acid and sugar ; sulphuric 

 acid and bichromate of potash ; nitric acid (sp. gr. 1 *3) ; cone, 

 hydrochloric acid ; ferric chloride. The reactions are best ob- 

 served when a few drops of a solution (in alcohol, ether, chloro- 

 form, etc.) are allowed to evaporate in a small dish and a drop 

 or two of the reagent added to the residue. In testing with sul- 

 phuric acid and sugar, it is generally better to mix the alkaloid as 

 intimately as possible with 5 parts of sugar and add the sulphuric 

 acid to the mixture. Delphinoidine should be mixed with as con- 

 centrated a solution of sugar as possible before the addition of sul- 

 phuric acid. If bichromate of potash and sulphuric acid are to be 

 used in combination, it is advisable to dissolve the alkaloid in the 

 acid and drop a crystal of bichromate into the solution. Sulphuric 

 acid and nitrate of potash may be employed in the same way in 

 place of the mixed sulphuric and nitric acids. Ferric chloride 

 should be used in aqueous solution, and be as neutral as possible. 2 



Some of these reactions might be used in testing for alkaloids 

 microchemically. The following table contains a few of the re- 

 actions of the more important alkaloids. 



1 Compare Schlieper, Annalen der Chemie und Pharm. Iviii. 357, 1846. 



2 All these reactions are described at greater length in my ' Ermittel. d. 

 Gifte.' 



