peared to be prussiate of iron. There can therefore remain no doubt respecting the existence of prussic acid in the produce of this distillation. But does this acid exist ready formed in cruciferous plants, or is it developed by means of heat, and of sulphuric acid?

These

are questions that cannot be resolved at present, nevertheless the first opinion appears to be by much the most probable.

C. Juice of woad from which the vegeto-animal matter had been separated by heat, was precipitated by acetate of lead; and a curd was obtained in large quantity, of a yellow colour, and formed of the vegetable acid formerly combined with lime (I. D and C), yellow extractive matter, green matter, and a small quantity of vegeto-animal matter that had escaped coagulation. This precipitate, on being decomposed by sulphuric acid, yielded a vegetable acid which possessed the following properties.

Upon evaporation, it became covered with pellicles, which proceeded from the re-action of the acid upon the extractive matter, &c. which was precipitated along with it. The greatest part of this substance was separated from it, by evaporating it several times, and then treating it with alcohol at 40°. The acid thus purified, and left to itself for a month and a half, did not crystallise; on being again dissolved in water, some flakes of yellow extractive matter altered by the acid were still separated, and the liquor possessed the following characters. Lime-water was not precipitated by it, but barytes water was, and the precipitate was totally redissolved in the water. These re-agents gave the acid a yellow colour, because it still retained a little yellow extractive matter. Concentrated potash deepened the co

lour,

lour, and no cream of tartar was produced, although there was a great excess of acid. Nitrate of barytes did not cause any precipitate, but one appeared on adding

a drop of ammonia. Muriate of lime yielded a precipitate soluble in cold water. Nitrate of silver, a precipitate soluble in nitic acid. Nitrate of quicksilver, and acetate of lead, white precipitates. The latter was soluble in acetic acid, but it required a certain quantity of the acid.

From these characters it would appear that the acid of the woad which is combined with lime, and is dissolved by water after the juice of woad has been treated with alcohol, is the malic acid.

The liquor being precipitated by acetate of lead, and afterwards treated with sulphuretted hydrogen, was evaporated. When it was sufficiently concentrated, it was put into a cold place, and after some hours, it yielded crystals of nitrate of potash. The mother water of these crystals was reddish, it contained much acetate of lime and acetate of ammonia, acetate of magnesia, acetate of potash, and a muriate. These salts were extracted by means of alcohol at 40°.

The residuum that was insoluble in alcohol was almost totally soluble in water, as only a white matter was left resembling starch, whose nature could not be determined on account of the small quantity of it. Was it not a salt similar to that supposed above to be a citrate ? The water had taken up gum, nitre, and lime, but with what acid the latter had been combined is unknown, The reddish colour of the solution did not arise from colouring extractive matter, because the acetate of lead and muriate of tin did not occasion any precipitate in it, It was probably owing to the re-action of the salts upon vegetable matter.

II. Ex

II. Examination of the Green Fecule left upon the Paper when the Juice was filtered.

(a) The greatest part of the green resin was extracted from this fecule by repeated macerations in alcohol while it was fresh. It was afterwards treated several times successively with boiling alcohol; by which means the wax, indigo, and green resin that remained were dissolved. The wax separated on cooling, and the indigo fell down at the end of a few hours. It sometimes happened that the wax drew along with it a little indigo. The following is probably the best method of separating these three bodies. The alcoholic liquor is filtered while boiling, the wax separates from it on cooling, it is again filtered and left exposed to the air, in about 15 or 20 hours the indigo precipitates on the sides of the glass. The liquor is then decanted, and the indigo washed with cold alcohol.

(b) The matter insoluble in alcohol is vegeto-animal matter retaining some indigo and green resin; and its quantity increases in proportion to the dryness of the fečula that is examined. Alcohol cannot dissolve these substances, because they adhere to it by the same power as causes indigo to adhere to woollen stuffs. Besides animal matter, the residuum also contains some remains of the wood of the plant.

When fresh made green fecula is treated with boiling alcohol, the green resin and indigo is taken up, but when the proportion of resin is very considerable, it retains much of the indigo in solution. To discover the presence of indigo in fecula, it may be treated with cold. alcohol, in order to dissolve the utmost possible quantity of green resin.

TO BE CONCLUDED IN OUR NEXT.

Specification of the Patent granted to RICHARD WILLCOX, of the Parish of Saint Mary, Lambeth, in the County of Surrey, Mechanist; for sundry Apparatus or Machinery for accelerating the Manufacturing of Felt or Stuff Hats, and for cutting and removing by Machinery the Furs of Beavers, of Rabbits, and the whole Variety of Skins, the Fur or Wool of which is used for the Purpose of Hat-making, Dated April 3, 1809.

With a Plate.

To all to whom these presents shall come, &c.

Now KNOW YE, that in compliance with the said proviso, I the said Richard Willcox do hereby declare that the nature of my said invention, and the manner in which the same is to be performed, is described and ascertained in the plans drawn in the margin of these presents, and the following explanation thereof; that is to say: My said invention consists of a method of holding down or confining the fur or wool during the operation of cutting or separating the fur from the pelt; and a method of VOL. XVIII-SECOND SERIES. Сс effec

effectually and conveniently removing the same after it is so cut or separated. My method of holding down the fur I thus describe: First, the skin being held down or confined to the surface of the roller on which it is advanced to the knife, I propose to hold or press down the fur by the application of an apparatus, which I call a drag (or some of the other similar suitable contrivances, which will be hereinafter described), moderately pressed on its surface; this is disposed either in a position parallel with or inclined to the axis of the large roller, is placed edgeways or inclined to it, may be composed of iron, of the other simple metals, of a composition of them, or of wood, and is either simple or compounded of different pieces, as the dimensions or other circumstances of the work may occasionally be found to require; and to this I add an apparatus which I call a rake, and by this I propose to remove the fur from off the pelt, after it is separated by the action of the knife; and the drag I construct so as to accommodate itself to and produce an uniform pressure or holding on the fur, notwithstanding its inequalities of thickness; and to produce this, I prefer and adopt an edge bar, pressing with its edge on the fur, and composed of three distinct parts, thus: two outer pieces form a case somewhat similar to that of a pocket comb, and a middle piece is placed between them, and projecting edgewise below them; this I make of about one inch deep and about one eighth thick, and its projection below the case about five eighths of an inch; it is secured to it by two or more rivets, one or two inches from each end, it is filed smooth on the edge which lies in contact with the fur, and this should be a little rounded; by this means the middle piece will, with a moderate degree of pressure, spring on its edge,

and