Dr. Guy, on Microscojnc Sublimates. 7 



marked with radiating or concentric lines, discs, prisms, 

 needles, and arborescent forms. 



7. Detached crystals blended with any of the foregoing 

 forms, and assuming the shapes of the crystals deposited from 

 solutions in alcohol, ether, benzole, chloroform, or fusel oil ; 

 — prisms, rosettes, groups of needles, square and oblong 

 plates, envelopes, and well-marked octohedra. 



S. Surrounding any of the foregoing sublimates a thin 

 mist, consisting of colourless globules, or a colourless waving 

 network; or the same discoloured by yellow or yellowish- 

 brown empyreumatic matter. 



Of the dark-feathered crystals of No. 4, 

 I may remark that they are such as gather 

 on the lip of a short reduction-tube, when 

 we adopt that mode of sublimation. Many 

 of them, in shape and colour, resemble 

 some of the finer crystals of the silver- 

 tree, obtained by placing a fragment of 

 zinc in a drop of a solution of nitrate 

 of silver (one grain to eight fluid ounces) 

 on a glass slide (fig. 2). 



The description which I have just given is such as any 

 person experienced in crystallization on the small scale, in 

 whatever way the crystals may be obtained, would have 

 expected. And I may state at once, as the result of large 

 experience of the sublimates of strychnine, that it would be 

 unsafe to infer their composition from their form. It can 

 only be stated, in general terms, that the compound crystals 

 of strychnine (the lattice- work especially) are generally built 

 up of elements arranged at right angles. Curved forms are 

 rare, and oblique arrangements also, except in the dark- 

 feathered or fern-like crystals of No. 4. 



But though we cannot infer the composition of the subli- 

 mate from its microscopic characters, we can draw certain 

 safe inferences from the incidents of the sublimation itself. 

 We have been dealing with a sparkling crystal, or particle of 

 white powder ; it has changed colour and yielded sublimates, 

 melted and yielded others, dried into a black spot of carbon, 

 and, in doing so, still yielded sublimates. I might add, that 

 the darkened and melted alkaloid did not travel over the porce- 

 lain slab, but left its black spot where the substance was first 

 placed. From these facts I infer that my crystal or speck of 

 white powder must be either an alkaloid, glucoside, or analogous 

 substance, or some substance of which we have at present no 

 knowledge, that also darkens, melts, yields sublimates, and 

 deposits carbon. And if, before I sublimed the substance, I 



