it might be found possible to increase the charge weight by steaming or by the employment of tamping devices. This small weight of charge constitutes one of the most serious objections to the use of hurds in paper manufacture.

In those tests in which the most satisfactory results were obtained, the cooking conditions were 29.5 per cent of caustic soda at a concentration of 107 grams per liter and a causticity of 84.0 per cent acting at a temperature of 170° C. for five hours, or a total time of seven hours. The steam condensation in the rotary used for these tests was abnormally high, due to the fact that the steam supply pipe was uncovered for a considerable distance and the rotary was entirely uncovered. It is believed, therefore, that a larger amount of caustic was necessary than would otherwise have been the case. This belief is strengthened by the quality of the waste liquor from one of the later cooks, which gave on analysis 16.85 grams per liter of free caustic soda and showed a causticity of 27.75 per cent. These data show that only 67.3 per cent of the total caustic employed was actually consumed in the cooking operation, which percentage is lower than obtains in practice. The stock from this cook was bleached with 11.5 per cent of bleach. But even as the figures stand, the comparison with poplar cooking practice is as follows: 29.5 per cent caustic soda used as against 22 to 25 per cent; 107 grams per liter as against 100 to 110; 84 per cent causticity is little different than obtains in practice; 170° C. is about commercial practice; five hours at pressure as against four to six hours; seven hours' total time as -23- against possibly six to eight hours; 11.5 per cent bleach as against 8 to 10 per cent. Thus, it is evident that the cooking conditions employed were slightly more severe and expensive than those in commercial use with poplar wood.

The yield of total fiber obtained from the hurds may be placed at 35 per cent of bone-dry fiber calculated on the bone-dry weight of hurds used, or 33.1 per cent of air-dry fiber calculated on air-dry hurds. The yield of bleached fiber was not determined in this preliminary work, but may be safely estimated as 30 per cent, which is low when compared with a yield of about 47 per cent of bone-dry bleached fiber from bone-dry poplar wood. It is believed quite possible that satisfactory cooking conditions may be found which will give a higher yield than was obtained during these tests. The stock should be classed as easy bleaching, and 11.4 per cent of bleach is a satisfactory figure, although a little high.

As to beating cost, in the last two and most satisfactory tests the total washing and beating time was three hours, which may be about an hour more than ordinarily is used in making papers of this grade, although the practice varies to a considerable extent.

In regard to furnish, there is such a diversity of practice that it is difficult to make a comparison, but if the hurd stock can be produced as cheaply as soda-poplar stock, the furnish used in these last two tests should be regarded as satisfactory to the book and printing paper manufacturer.

The finish of the paper was not all that might be desired, but that was due almost entirely to the calender stack available for the work, which was composed of nine light rolls, many of which were about 6 inches in diameter and which had not been reground for some time. From a small test on a large calender stack it was readily shown that the paper produced is capable of taking a satisfactory finish.

This comparison, satisfactory in many respects, develops two factors which are decidedly unfavorable to hemp hurds, namely, raw-material storage and digester capacity, and they must be taken into full account in considering the paper-making value of this material, although it should be recognized that investigation may result in the material improvement of these conditions. Moreover, it is not at all improbable that further investigation would develop more satisfactory treating conditions and more suitable furnish compositions, and the belief in this possibility is strengthened by the fact that material progress was being made at the conclusion of this preliminary work.

Calculations on the raw material and acreage for a permanent supply for a pulp mill producing 25 tons of fiber a day for 300 days per annum, or 7,500 tons per annum, give the comparison between hurds and wood shown in Table II.

-24- Table II.—Comparison between wood and hemp hurds.

The most important point derived from this calculation is in regard to areas required for a sustained supply, which are in the ratio of 4 to 1. Every tract of 10,000 acres which is devoted to hemp raising year by year is equivalent to a sustained pulp-producing capacity of 40,500 acres of average pulp-wood lands. In other words, in order to secure additional raw material for the production of 25 tons of fiber per day there exists the possibility of utilizing the agricultural waste already produced on 10,000 acres of hemp lands instead of securing, holding, reforesting, and protecting 40,500 acres of pulp-wood land.

The annual growth per acre, although decidedly in favor of hurds, has little bearing on the project, because the utilization of the hurds is subordinate to the raising of hemp, and the paper manufacturer probably could afford to use only hurds resulting from the hemp industry.