SUBLIMATION OP ALKALOIDS. 73 i 



water of crystallisation as quickly as possible, by the 

 aid of a spirit lamp ; then with a Bunsen's burner bring 

 the plate to a high temperature. Immediately a remark- 

 able change is seen to take place in the form of the crystal, 

 and if properly managed the " foliation " represented in 

 the plate will be fairly exhibited. The slide must not be 

 allowed to cool down too rapidly or the crystals will 

 probably absorb moisture from the atmosphere, and in so 

 doing the crystals alter their forms. Immerse them in 

 balsam, and cover in the usual way before quite cold. 



Sublimation of Alkaloids. Dr. Guy a few years ago 

 directed the attention of microscopists to the fact that the 

 crystalline shape of bodies belonging to the inorganic 

 world might lead to their detection. Subsequently, Dr. 

 A. Helwig, of Mayence, took the matter up, and showed 

 that the plan was applicable not only to inorganic but also 

 to organic substances, and especially to the poisonous alka- 

 loids. By improving on Dr. A. Hel wig's process, and 

 substituting a bit of porcelain, Dr. Guy has been able to 

 watch the process more minutely, and to regulate it more 

 -exactly. He has by this means been able to obtain 

 characteristic crusts composed of crystals of strychnine 

 weighing not more than l-3,000th or 1 -5,000th of a grain. 

 Morphia gives equally characteristic results. For the 

 examination of these, Dr. Guy recommends the use of a 

 binocular microscope with an inch object-glass. But it is 

 not to crystalline forms alone that one need trust; the 

 whole behaviour of a substance as it melts and is converted 

 into vapour is eminently characteristic, and when once 

 deposited on the microscopical slide, under the object- 

 glass, the application of re-agents may give still more satis- 

 factory results. The re-agents, however, which are here to 

 be applied are not of the kind ordinarily employed. Colour- 

 tests under the microscope are, comparatively speaking, 

 useless : those that give rise to peculiar crystalline forms 

 are rather to be sought after. For instance, the crystals 

 produced by the action of carbazotic acid on morphia are 

 by themselves almost perfectly characteristic. These ex- 

 periments should not, however, be undertaken for medico- 

 legal purposes by one unskilled in their conduct, for the 

 effects of the re-agents themselves might be mistaken by 



