produce its maximum content of sugar in areas where the mean temperature for the three months of June, July, and August rises above 70 degrees F. The southern limit of this area is an irregular, waving line, as indicated in the accompanying map (Fig. 69). There are, of course, localities where highgrade beets can be produced south of this line, but in point of fact nearly every successful beet sugar enterprise has been located within the field indicated. There is really no limit to the northern edge of this belt except that of short seasons, incident to late frosts of spring and early frosts of autumn. To successfully compete in the sugar markets of the world the sugar beet should enter the factory with an average percentage of sugar of not less than

12.

Very much richer beets are often produced and in some of the irrigated areas of the west, where the climate is remarkably dry, an average percentage of 16 and 18 even has been obtained. In the whole beet sugar crop of the United States the average percentage of sugar in the beet is probably not far from 13 or 14. In this respect it is seen that the beet is richer in sugar than the average sugar cane of Louisiana, which does not contain over 11 or 12 percent of sugar.

Yield per Acre.-The average yield per acre of sugar beets in the United States is unfortunately very low, due chiefly to ignorance of the proper method of culture. The sugar beet is more of a garden than a field crop and requires special cultivation and fertilization. The average yield in the United States

has probably not exceeded eight tons per acre, while the average yield in Europe is twelve or thirteen tons per acre. In this respect the Louisiana sugar cane has a marked advantage, the average crop being over twenty tons, while thirty and even forty tons are often obtained. As soon as our farmers learn the principles of culture it is certain that the average yield in the United States will be as great as that in Europe. A typical field of beets ready for the harvest is shown in Fig. 70.

Manufacture. The manufacture of beet sugar is both a simple and a complicated operation. The simplicity of it consists in the fact that it is only necessary to extract the saccharine juices of the beet, properly clarify

them, and reduce them by evaporation to a point where the sugar will crystallize. In reality the operation of successful manufacture requires elaborate and costly machinery and a high degree of technical skill. A brief outline of the method will be sufficient for the purpose of this manual.

The beets, after harvesting, have the tops cut off with a small quantity of the adhering material of the neck of the beet, which contains large quantities of salts and is not suitable to enter the factory. In Fig. 71 is shown a view of a beet field after the harvest. The beets are then thoroughly washed and passed through a slicing machine in which they are cut up into thin slices or ribbons. They then enter a series of tanks, known as a diffusion battery, in which they are thoroughly treated with hot water, by means of

which practically all of the sugar which they contain is extracted. The saccharine product obtained, known as the diffusion juice, is treated with a

FIG. 72.-DIFFUSION BATTERY.-(Farmer's Bulletin 52.)

large excess of lime, heated, and carbonic acid derived from a lime kiln blown through it until the lime is all converted into a carbonate carrying down with

BEET SUGAR.

463 it the impurities of the juices. The diffusion juice as it comes from the diffusion battery is usually almost as black as ink. After carbonatation, as the process above is called, it is of a clear, light amber tint. To separate the liquid from the solid matter the whole is passed through a filter press from which the juice emerges bright and clear and the carbonate of lime with its adhering impurities remains in the filter press as hard cakes. This process is repeated in order to secure as great a purity as possible in the juice.

Evaporation. The purified juice is conducted into multiple-effect vacuum pans, Fig. 73, from which the air is partially exhausted by a pump, the vacuum rising in the series. There are usually three or four of these pans connected to

FIG. 73.-MULTIPLE-EFFECT EVAPORATING APPARATUS.-(Farmers' Bulletin 52.)

gether, the first one having the least air exhausted from it and the last one the most, that is, having the highest vacuum. The vapor which arises from the first pan is conducted through the copper coils to the second and serves as the heating agent while the vapor from the second pan passes through the copper coils to the third and so on to the fourth. Thus the steam used for evaporating is turned only on the first pan and by this means a great economy in the use of fuel is secured. In this way the juice is evaporated to a sirup. This is usually somewhat colored and if white sugar is made it is bleached by passing through bone-black or by the application of sulfur fumes. When sulfur is used it is often applied first to the unevaporated juice as well as to the