Albumen may be prepared in a pure state from white of eggs,by the following method: - The white of eggs is beaten up well with water and filtered. To the filtrate is added a small quantity of sub-acetate of lead, in order to remove the mineral substances. The whole of the albumen is now precipitated as albuminate of lead. This is stirred up with water, and carbonic acid gas is passed through, by which the albuminate of lead is decomposed; carbonate of lead is precipitated, and the albumen remains in solution. The carbonate of lead is now filtered off through paper which has been washed with dilute acid. Traces of lead still remain, and to remove these the filtrate is treated with a few drops of aqueous sulphuretted hydrogen, and gently heated. The first flocks of albumen which appear, retain the whole of the lead as sulphide. This is filtered off, and the filtrate evaporated gently in a basin, the residue consisting of pure soluble albumen.
The manufacture of egg-albumen in the neighbourhood of Moscow, is carried on in the houses of the country people, who bring their product to the town in small quantities. The albumen is generally roughly prepared and of bad appearance, and often spoils. But egg-albumen is produced on a manufacturing scale in the neighbourhood of Korotscha, the largest establishment there numbering 60 to 70 workwomen, and having used 8 million eggs, producing about 1500 pud (of 36 lb.) albumen, of the value of 60,000 rubles. In the same place are two smaller establishments, one employing 20 to 30 women, and treating about 21/2 to 3 million eggs yearly. In 1880, the production did not come up to the demand, on account of the scarcity of eggs, and the price rose from 37 to 40 rubles (of 2s. 6d.) per pud in 1879, to 54 to 55 rubles in 1880. The yolks of the eggs are mostly exported to Germany, where they are used in the preparation of glove - leather, sometimes under the name of "egg-oil."
In preparing egg-albumen there is considerable difficulty in completely separating the white from the yolk. Campe recommends that the whites should be refined by whipping up with oil of turpentine and a trace of acetic acid, and allowing the whole to stand for 25 to 36 hours, when the oil floats on the surface, and carries impurities with it. From a pecuniary point of view, this process does not appear to be advantageous, at least not in Moravia, Silesia, and Saxony. An important condition for the profitable production of albumen from eggs is the possibility of easily disposing of the yolk. Since this cannot always be done in the neighbourhood of albumen factories, and as transporting the material to a distance is apt to produce decomposition, it is necessary to add to it some antiseptic substance. Campe finds a solution of soda arsenate in glycerine, to which some salt is added, best suited for the purpose. Carbolic acid, soda hyposulphite, etc, have been more or less suc-.-cessfully tried, but found objectionable on the part of tanners and glovers, who are the chief consumers of yolk of egg.
The former imparts to the leather its penetrating smell, the latter produces stains.
Desiccated egg-albumen is now well-known in the market in the form of a powder, costing about 1s. per 3 1/2 oz., this quantity representing the whites of about a score of eggs. For use in photography, 3 teaspoonfuls of cold water added to every 1/2 teaspoonful of powder represent the normal consistency of egg-albumen.
According to Berg's process for preserving egg-albumen for photographers, the whites, separated from the yolks, are evaporated to dryness in zinc or porcelain basins, at a temperature of 113° F. (45° C), the operation being conducted in vacuo, to hasten the evaporation. The solid albumen thus obtained is reduced to powder, which, if kept perfectly dry, may be preserved for a long time without alteration, and is applicable to all ordinary purposes.
Fish-albumen is not unknown in the market, and may be recognized by its fishy odour. Hilman's process for preparing it is as follows: - The crushed spawn is macerated in sufficient water to dissolve out the albumen. The albuminous water is separated by filter press, and evaporated in a vacuum-pan nearly to dryness. The thickened mass is then dried on drying-floors, salicylic acid, in the proportion of 1 to 20, being added as a preservative. There are difficulties in the way of freeing fish-albumen from accompanying substances, which reduce its value.
Vegetable - albumen is most easily prepared from potatoes, by cutting them into slices, covering them with very dilute sulphuric acid (2 per cent.), leaving them 24 hours, then adding fresh potatoes, and repeating the operation once more, afterwards neutralizing with potash and boiling. A considerable quantity of albumen is then deposited in thick white flocks. It can also be made from wheat-flour and from oleaginous seeds. Kingzett's and Portheim's processes, briefly alluded to under "Blood-albumen," are equally applicable to gluten, the protein of worts, etc. The latter inventor takes 100 lb. of the albuminous matter, ground up and washed with water, and dissolves it in 200 to 250 lb. of water, in which has been previously dissolved 4 lb. of caustic soda or potash at 194° to 212° F. (90° to 100° C). To the solution thus prepared he adds 4 per cent, of a solution containing 40 per cent, of glycero-sulphate or glycerophosphate of calcium, or 4 per cent, of a mixture of calcic chloride and an alkaline salt of citric, tartaric, or meta-phosphoric acid.
The mixtures arc " scaled " in the usual way.
No commercial attempt seems to have been made to prepare vegetable-albumen from the waste of starch factories and oil-presses, though there would seem to be no insuperable difficulty. The subject is well worth attention, for the raw materials would be cheap as compared with eggs, blood, or fish-roes, and, moreover, of no value for alimentary purposes. This appears to be the only promising direction in which an increased production of what has become an indispensable article can be looked for.