178 ALKALOIDS. 



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

 precipitate it from aqneons solutions. 



g 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.i 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 i^roducing colour-reactions with alkaloids : Pure 

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

 200) ; sulphuric acid, containing 0*01 gram of molybdate of soda 

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

 acid and bichromate of potash ; nitric acid (s^». 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 comljination, it is advisalile to dissolve the alkaloid in the 

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

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

 ])lace of the mixed sulphiu-ic and nitric acids. Ferric chloride 

 shoiüd be used in aqueous solution, and be as neutral as possible.^ 



Some of these reactions might be used in testing for alkaloids 

 microchemically. The following tal)le contains a few of the re- 

 actions of the more important alkaloids. 



' Compare Scliliepur, Annalen fler Chemie imd riiarm. Iviii. 3.^)7, 1846. 

 - All these reactinns are (l(;.Hcribed at greater length in my ' Ermittel, d. 

 CJifte.' 



