ON AN APPLICATION OF DIALYSIS. 
213 
scope they were found to be six-sided and to twist a ray of plane polarized light, 
were not volatile, gave a violet tint to flame, and deflagrated on charcoal; their 
aqueous solution gave a yellow crystalline precipitate with bichloride of platinum, 
no odour on heating with caustic alkali, a black colour with sulphate of iron and 
sulphuric acid, and yielded ammonia on heating with potash, zinc and iron. It 
was deemed desirable to apply all these tests in this and similar examinations, as 
a pound of vegetable seldom yielded more than a few grains of crystals, a quan¬ 
tity sometimes too small to purify by recrystallization, and always too small to 
admit of the production of strongly marked analytical reactions. In the case 
of potato however I went to the trouble of operating upon thirty or forty pounds 
of the tops and thus obtained about the same number of grains of nitrate of pot¬ 
ash, and the extra labour was rewarded, for the mother-liquor of the nitre, after 
standing aside two or three days, yielded a small crop of beautiful little crystals, 
of which I can at present say but little more than that they were not nitrate of 
potash. They were perfect little hexagons, not much longer than broad, with 
flat heads ; I suspect them to be a magnesium salt. Besides these constituents, 
the juice of potato yielded cubes, hollow pyramids, and prisms of chloride of po¬ 
tassium, much ammonia and sugar, even immediately after expression, and other 
matters, the nature of which was not ascertained. 
Atropa Belladonna. —The leaves and soft parts of the Deadly Nightshade also 
yielded nitrate of potash by the above process. But in addition some acicular 
crystals, single and in tufts, were obtained. These were carefully separated from 
the nitre crystals and were recrystallized. They were then found to be square 
prisms, neither deliquescent nor efflorescent, and containing magnesium as the 
sole inorganic constituent. The nature of the organic matter associated with 
the magnesium, could not be ascertained, apparently it was not any of the ordi¬ 
nary organic acids. The juice of Belladonna also contains ammonia, a matter 
which reduced copper salts as sugar does, and other bodies not examined. 
Pisum sativum .—Several quarts of peas, in the shell, were similarly treated. 
The product was a thick syrup of light-brown colour, yielding no crystals even 
after the lapse of several weeks. The ash of a portion of it gave a pure po¬ 
tassium tint to flame, and its solution a slight chlorine reaction. Ammonia 
was also evolved on heating the diffusate with potash, but no nitric acid could 
be detected. Apparently, therefore, the fruit of the pea contains no nitrate 
of potash, and only a minute quantity of any inorganic crystalline salt. The 
chief organic crystalloid is obviously sugar. 
Lactuca sativa. —Half-a-dozen large garden-lettuces were next submitted to 
the process. Here, again, the concentrated diffusate yielded nitrate of potash. 
The crystals were however mixed with many perfect tetrahedra, but in quantity 
insufficient to admit of chemical analysis. The mother-liquor contained sugar 
and ammonia. 
Cucumis sativus. —Several cucumbers were then operated on. They furnished 
a diffusate, of which the chief constituent was sulphate of lime, but it also gave 
reactions indicating sugar, and the juice, immediately after expression and 
again after dialysis, yielded ammonia on warming with dilute solution of 
potash. 
Brassica oleracea. —The juice of three or four cabbages, treated in like 
manner, also gave a diffusate, from which much sulphate of lime separated on 
evaporation. It also yielded ammonia when heated with fixed alkali, but be¬ 
sides sulphate of lime no crystals were obtained from it. 
Datura Stramonium .—This plant, the Bitter Thorn-apple, I found to contain 
so much nitrate of potash that a dried portion quite deflagrated on being 
burned in a muffle. 
From these few experiments it is, I think, obvious that this application of 
Graham’s beautiful process of dialysis promises to be of great service in inves- 
