33. On a New Vegetable Acid.
34. Altheine, a new Vegetable Principle.
35. Rheine, a new Substance from Rhubarb.
36. On Dragon’s Blood, and a new Substance which it contains, by M. Melandri.
Supposing that this substance might contain a principle analogous to that latterly observed by M. Pelletier in logwood, &c. a portion of it was dissolved in strong alcohol, the solution evaporated until very concentrated, and then poured into cold water, an agglomerated spongy substance was precipitated, which, after being washed with cold water and filtered, was triturated with water containing 1100th of sulphuric acid, and exhibited traces of chemical action at a temperature of 22° (61°.6 F.) It then deposited a substance upon the sides of the vessel, and the liquid became yellow and very acid. The sediment, being carefully washed with water, was of a fine red colour, varying according to the state of aggregation; it had no taste or smell; was flexible between the fingers, and was quite fluid at 55° (131° F.). This substance, which the author has called Dracine, has some analogy with the vegeto-alkalis, although its affinity for acids is but slight. The sulphate may be obtained, he says, by adding sulphuric acid diluted with alcohol to an alcoholic solution of dracine, precipitating the mixture by cold water, and then applying a little heat; the sulphate of dracine collects at the bottom, is to be washed with cold water until the latter no longer reddens litmus paper, and then dissolved in hot water. This solution becomes red by the smallest quantity of alkalis, and may be used as a very sensible test of their presence. Dracine is also a good test for acids, assuming a yellow colour with them. The small quantity of carbonate of lime in filtering paper may be detected by sulphate of dracine, the yellow solution instantly becoming red from its action, and thus showing its presence.—Bull. Univ. C. xi. p. 157.
37. Purification of Madder, by the Separation of its Yellow Colouring Matter.
On commencing the operation, 50 or 55 lb. of pulverised madder are to be put into the first vessel, water is to be added, and stirred into the mass until it stands 112 inch above the madder. The whole is then to be left until fermentation comes on and has formed a coat of madder at the surface; this usually takes place in 36 hours, and at latest in 48 hours, according to the temperature. The mass should now be transferred into the second vessel, which is then to be filled with water, and being left for two hours, the madder will fall to the bottom. The upper cock is then to be opened, after that the second, and then the third; and the water which runs from the two latter is to be put into the third vessel, that the rest of the madder may separate from it. The madder in the second vessel is then to be washed a second, third, or fourth time until the washing water is colourless. Thus purified, the madder may be used in the processes of dyeing, according to the known methods; but it is important in summer that it should be used immediately, that a new (the vinous) fermentation may be avoided. The madder deposited in the third vessel, when washed and deposited, may be used like the rest. The liquid first separated after the fermentation may be used in the preparation of hot indigo baths, &c. instead of madder.—Bull. Univ. P. vii. 352.
[36] See page 239 of the last volume.
38. On Indigo and Indigogene, by M. Liebeg.
This white substance was called Indigogene. It did not change colour in dry air, but under water became of a deep blue, which by drying, assumed a coppery appearance. The blue substance volatilized by heat without leaving any residue, forming purple vapours, which condensed, when cold, into crystals differing in nothing from sublimed indigo. Indigogene dissolves in alkalis without neutralizing them: it is also soluble in alcohol, but insoluble in water or acids.