Campe recommends that the dishes and sieves for the separation of the serum should be in close proximity to the slaughter-houses, since the retarding of that separation is almost sure to be followed by more or less coloration of the serum, which, of course, leads to a dark-hued albumen.

The blood clot is cut into small lumps, placed on the sieves, and left there for 40 to 48 hours. The first portions of the serum which pass through arc always red, but after the lapse of about an hour, the percolating liquid shows a clear yellow colour, the tinge varying, according to the variety of the cattle, from deep gold to that of pale hock. After 48 hours, the clear serum is drawn off, care having been taken that the lowest layer containing the red blood-corpuscles is kept back. About 25 to 30 per cent, of serum is thus obtained from ox-blood, and this raw material can be manufactured into either the so-called "natural" albumen, without gloss, or the "patent" glossy albumen.

In making natural albumen, J lb. of oil of turpentine is added to 100 lb. of serum, and the whole is whipped for an hour with apparatus similar to the dasher of an old-fashioned churn. The turpentine not only bleaches the serum and extracts the grease/but also helps to preserve it. It is allowed -24 to 36 hours to settle, when the clear serum is drawn off from the sediment. The drying is done in japanned iron dishes 1 ft. long, 6 in. wide, and 3/4 in. deep. The temperature is at first about 122° F., and is raised to nearly 135° F. (57° C.) for 2 hours, after which it is allowed to fall to 118° or 120° F. (48° to 49° C). The drying occupies about 36 hours.

The manufacture of "patent" albumen differs from the above in the use of acids. To 100 lb. of serum are added 7 dr. sulphuric acid, mixed with 6 1/2 oz. concentrated acetic acid, and 6 lb.water; J lb. oil of turpentine is next mixed with it, and the compound is whipped for an hour. After settling for a day or more, the clear liquid is poured off, neutralized with ammonia, and dried as before. About 10 lb. of serum will yield 1 lb. of dried blood albumen.

Both these preparations are called "primary" products, as distinguished from the " secondary " and " tertiary " products obtained from the residues left in the dishes after the drawing off of the pure serum and from the clot on the sieves. The albumen from the last-named source is, of course, of very inferior quality, but is largely used in sugar refining.

Blood-albumen, of good quality, is manufactured near St. Petersburg, in an establishment close to the central slaughter-house, so that the serum is obtained quite fresh, and is brought at once into the drying rooms. The blood-albumen produced in other parts of Russia is not of so good a quality as that prepared in St. Petersburg. There are three large blood-albumen works in Moscow, which are, however, situated at some distance from the slaughterhouses. The prices vary a good deal - from 15 to 30 rubles (of 2s. 6d.) and even 40 rubles, per pud (36 lb.). The St. Petersburg brand is sold always 5 to 10 rubles higher than the others. St. Petersburg produces yearly 4000, Moscow 2000, and the other towns about 1300 puds, so that the whole production is about 7300 puds. In the albumen factories at Buda-Pest, 3000 lb. of blood are expected to yield about 110 lb. of albumen, at a cost somewhat less than 1/3 that of egg-albumen. The manufacture there is extensive.

The manufacture of blood-albumen is pretty largely carried on in this country of recent years, and is the subject of some interesting remarks from Dr. Ballard, especially with regard to the noxious effluvia arising from it. The trade consists in the separation of the serum from blood-clot, and the drying of the former into transparent flakes of a reddish-yellow colour, but varying in depth of colour according to the quality of the serum from which they are made. Blood-clot is absolutely worthless for the purposes of this trade if it be not fresh. The more recently the blood has coagulated, the more valuable it is for albumen making. Hence the blood-albumen makers effect arrangements for the speedy collection of blood from butchers and town abattoirs, and it is dealt with immediately on its arrival at the works. Sometimes the first process, that of "separation" of the serum from the clot, is carried on in some part of a public abattoir. The serum is, in such cases, sent away in casks to the establishments where it is dried.

The .blood arrives in the shallow iron vessels in which it is caught from the slaughtered animals, or in casks. The clot is immediately taken out and carefully sliced (when it arrives in shallow vessels it is sliced before removal from them), and the slices are arranged upon iron strainers, each with a pan beneath to receive the serum which flows out as the clot continues to contract spontaneously. The season of the year governs the time during which this draining is prolonged. In summer it is continued for about 12 hours, but in winter for 18 or 24 hours. The strainers, each with its pan beneath, are arranged on racks in a building which is so constructed as to be kept as cool as possible. It is also important that the building should be in such a locality as to be free from vibration caused by the passage of heavy vehicles or railway trains. From the pans, the serum is, in the best works, transferred into a settling tank, where it remains about 2 days until all the red colouring matters, etc, which may be in suspension having been deposited.

At some works, where an inferior article is made, the highly-coloured serum which comes with the clot in the casks is dried, and after the clot has been drained, it is put into a cask (from which the head has been taken out) to separate in bulk still further, and the dark serum which exudes is run off for use.

The serum is then transferred into a series of shallow iron trays, which are arranged upon racks in a chamber heated with steam pipes to a temperature of about 120° F. (49° C). When it is quite dry and brittle, the albumen is scraped from the trays, and taken to the warehouse to be sorted and packed. The waste clot usually is sent away either to the manure maker or to the blood driers, but is sometimes dealt with on the spot.