210 ODOROGEAPHIA. 



quite loose. The different menthol cones which have been 

 produced commercially, may be classed under five heads : — 



1. Cones prepared from pure menthol, that is, menthol havinp^ a 

 melting point of 42^-2 C. The characteristics of these cones are 

 that they are hard, and when scraped with the finger-nail feel 

 gritty and stone-like. When rubbed on the skin they are 

 susceptible of a high polish. The cone is completely soluble in 

 alcohol and a small piece heated in a test-tube melts very readily. 



2. Cones that have been prepared with menthol that has not 

 been completely freed from oil of peppermint. These are recognised 

 by their comparatively strong odour of peppermint and by their 

 melting point being under 42^-2 C. 



3. Cones made of w^ax, stearin, cetaceum, or paraffin, with 

 varying proportions of menthol. The menthol used in this class 

 has not, as a rule, been freed from oil of peppermint. These, when 

 scraped with the finger-nail, have not the stone-like grit character- 

 istic of the first class, but feel soft and yielding, and small pieces 

 readily peel off. When a small portion is heated in a test-tube, a 

 little is melted from the outside, and the remainder floats in the 

 liquid thus formed, at the same time slowly dissolving. A frag- 

 ment placed in cold alcohol does not dissolve ; if the cone has a 

 larger percentage of menthol than w^ax, etc., the edge of the frag- 

 ment becomes fringed, owing to the menthol dissolving out and 

 leaving the wax which was disseminated throughout the cone as a 

 framework ; but if the wax be in excess the alcohol has no visible 

 effect. If the alcohol be heated the fragment liquifies ; the 

 menthol dissolves in the alcohol, and the wax solidifies on cooling. 

 The proportions of both may in this way be determined. 



4. Cones consisting of menthol, with the addition of some 

 powder as an adulterant. These are recognised by simply rubbing 

 them on the skin, when they impart a feeling as if the latter were 

 being rubbed with pumice-stone soap. This is owing to the 

 menthol dissolving out and leaving the grains of insoluble powder 

 sticking on the cone like the pumice-stone in the soap. 



5. Cones which may belong to any of the above classes, but 

 which contain in addition a small percentage of eucalyptol, 

 thymol, benzoic acid, or other irritant. The distinguishable feature 

 of this class is the intense prickling sensation experienced when 



