Potassa bichromate

Winckler Has given the following recipe for a green ink —Dissolve one hundred and eighty grains of bichromate of potassa in one fluid ounce of water add to 1 the menstruum, while warm, half an ounce of spirit of wine then decompose the mixture with concentrated sulphuric acid until it assumes a brown color. The liquor is now evaporated till it is reduced in quantity to one-half, when it ie diluted with two ounces of distilled water, filtered, mixed with half an ounce of alcohol, subsequently with a few drops of strong sulpliurio acid, and then allowed to rest till, after some time, it assumes a beautiful green color. It is finally adapted for use by the addition of a small quantity of gum-arabic. 

Perrot, reviewing the process of Heidenreico, directs twenty drops to be employed and. instead of the glass-plate and white paper, he uses capsules of white porcelain. In tho place of sulphuric acid, he used also a saturated solution of bichromate of potassa in this acid, and in the proportion indioatod above, namely, one drop to twenty of oil. In applying this method, it is always nocessary, to insure greater certainty, to compare the effects upon tho oil to bo examined, with an oil the purity of which is undoubted. The appended table shows tho reactions produced by sulphuric acid alone, and by the solution of bichromate in tho acid —... 

Morphin is often contaminated with narcotic, which may be entirely removed by ether, or the impure mass may be treated with very dilute acetic add which dissolves the former, leaving the latter untouched. To determine the purity—from nareotin—of any sample of morphin, it may be dissolved in hydrochloric acid, and treated with caustic potassa in excess, in which the morphia will entirely dissolve, while any narcotin present remains untouched. If a very small portion of morphia is placed in a watch-glass with, a little pure sulphuric aoid and au equal quantity of water, and if a particle of bichromate of potassa be added, a nickel green color appears, which changes, first to a copper green, and finally, to a dark dirty green. 

The sensitive coating for receiving tho image, is prepared by adding to about a quarter of an ounce of gelatin, dissolved in eight or ton ounces of water, by the aid of heat, one ounco, by measure, of a saturated solution of bichromate of potassa in wator, and straining... 

Bichromate of Potassa.—This salt js of groat importance in the arts and manufactures, and especially in calico printing. By a reference to the article on Dyeing, Vol. L, page 643, et eequitur, the reader will ho come acquainted with the variety of purposes to which it is applied in this most useful and beautiful art. The principal manufactories of the bichromate or chrome are at Glasgow. It is obtained from the salt last described by adding a sufficient quantity of acid— usually sulphurio—to impart to the solution a sour... 

Bichromate of Lead—2 PbO, CrOj— chrome red— may bo obtained by boiling oxide of lead, or its car-bonato, with on aqueous solution of monochromate of potassa, or by digesting the neutral chromate of lead in a dilute solution of caustic potassa. Liebig prepared it by adding a neutral ebromate to fased nitre, and washing the residuum it is an insoluble, scarlet colored powder. 

Synonyms Bichromate of potash, Bichromate of potassa, Potassium dichromate, Red chromate of potash, Red chromate of potassa. 

To Obtain C omic Acid. Take to measures of a saturated cold solution of bichromate of potassa, mix with it 15 measures sulphuric acid, and allow the mixture to cool. The chromic acid is deposited in crystals, which, after decanting tho mother liquid, are placed on a tile to drain, covered vrith a bell glass. 

Instead of using lijdrochloric acid, 40 lbs, of sulphuric acid and 60 lbs. of common salt may be used. Ihe sulphuric acid is diluted with about twice its hulk of water, and the salt, preTiously dissolved in cold water, is mixed with the Bolution of bichromate of potassa in the proportion given. Some persotis, in bleaching palm-oil by the above process, have been known to use as much as 40 lbs. of bichromate to the ton, an excess not only extravagant bat unnecessary. 

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