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DYEING AND CALICO PRINTING.

add reaction. Albumen as it occurs in the organic bodies of animals andplants is soluble in water; but under the combined a&ion of heat and wateralbumen becomes entirely insoluble without any perceptible alteration in com-position. This very characteristic molecular change is termed coagulation,and is one of the most important properties of albumen. Pure albumen,entirely deprived of the salts and alkalies, which in the natural state accompanyit, begins to coagulate at 59*5° C., the change being indicated by a slightturbidity. The turbidity increases with the temperature up to 63° C., whenthe formation of a flocculent mass commences, complete solidification ensuingat 75 0 C.

The native solutions of albumen—for instance, white of egg—contain abouti - 5 per cent of soda. These solutions do not on coagulation form a flocculentmass, but become gelatinous; the coagulation is never complete, owing tothe fadt that a portion of the nitrogenous matter remains soluble under theadtion of the alkali. If there occur a large excess of alkali coagulation doesnot take place even at 100° C. The adtion of carbonated or of caustic alkaliupon albumen is precisely similar.

Albumen enters into combination with baryta, strontia, and lime, formingtherewith insoluble compounds, which when dry are exceedingly hard. Thelate Dr. Gerhardt held the view that albumen is a bi-basic acid, white of eggand serum of blood containing the acid albuminate, while the coagulationobtained under excess of potassa represents the neutral salt. M. Lassaignehas shown that there can be produced double salts of albumen (or morecorredtly albumine, since albumen is albumine plus certain salts and soda),having sodium and copper as bases.

Albumen is coagulated, that is, converted into albumen insoluble in water,by most of the mineral acids, and readily by nitric acid at the ordinarytemperature of the air. Pyrophosphoric and normal phosphoric acid, as wellas the vegetable acids, do not coagulate albumen. Alkaline salts added to asolution of albumen do not effedt any change at the ordinary temperature ;but as the quantity of these salts is increased the coagulation of the albumenby heat is retarded. Ferrocyanide of potassium, yellow prussiate of potassa,precipitates in the cold all solutions of albumen after the previous addition ofsome acetic acid. An excess of acetic acid causes the precipitate to bedissolved. If an excess has been added accidentally, the application of gentleheat will effedt the precipitation of the albumen. Bichromate of potassaprecipitates albumen in the presence of vegetable acids. Several metallicsalts, as sulphate of copper, bichloride of mercury (corrosive sublimate),nitrates of lead and silver, as well as alum, precipitate albumen from solutionor from the solution of an alkaline albuminate. But the precipitates thusthrown down are generally soluble in an excess of the precipitant. Con-centrated alcohol in excess at once effedts the coagulation of albumen ; dilutealcoholic solutions have the effedt of retarding the coagulation of albumenby heat. Tannic acid, aniline, creosote, carbolic acid, and other organic sub-stances possess the property of coagulating albumen.

Coagulated albumen is a white, opaque substance exhibiting an acid readtionto test-paper. After drying, coagulated albumen becomes yellow, transparent,horn-like, and very brittle; in this state it readily absorbs moisture, beingthereby increased in bulk. It is insoluble in cold water, becomes liquefied by