CHEMICAL TOXICOLOGY, 295 



It is the habit of many writers on toxicology to carefully 

 tabulate and compare the kind of such precipitates given 

 by the alkaloids. This is entirely useless for the detection 

 of traces recovered from organs, although possibly valuable 

 when detecting a pure substance. Since the residues got 

 in the laboratory are always, even when once purified, 

 contaminated with basic animal products, they always 

 give a positive reaction with all or some of the general 

 reagents, and the use of these agents therefore misleads, 

 wastes material, and is seldom resorted to. 



Glucosides. — These compounds are all characterised by 

 yielding sugars (generally glucose) on contact with mineral 

 acids, and thereon is based the Brunner-Pettenkofer test, 

 which is a modification of Pettenkofer's well-known bile 

 test. A solution of the suspected substance is made in 

 water along with a little purified ox-gall and placed in a 

 test-tube. Strong sulphuric acid is poured down the side 

 of the tube, forming a heavy layer below the water-bile 

 solution. At the point of juncture there is developed a 

 cherry-red colour zone, which gradually extends through- 

 out the aqueous layer. Its formation depends on the split- 

 ting off of sugar from the glucosides, thus giving with 

 sulphuric acid the bile reagent of Pettenkofer's test. 



Unfortunately, residues often contain traces of carbo- 

 hydrates, and thus the test fails, unless the glucoside has 

 been obtained in sufi&cient quantity to permit of purification. 



Sulphuric Acid as a Reagent for Alkaloids and Glucosides 

 is of some value, although the indications are apt to be 

 misleading when the material is not pure. A test per- 

 formed either with pure sulphuric acid, or with sulphuric 

 acid containing a small proportion of an oxidising agent, 

 such as nitric acid (Erdmann's reagent), molybdic acid 

 (Frohde's reagent), vanadic acid (Mandolin's reagent), can 

 only be taken as a guide, and must be confirmed by special 

 characteristic chemical tests, or, failing these, by a physi- 

 ological experiment. 



The appended table sets forth the colorations given by 

 some of the important alkaloids and glucosides, the order 



