I N D UXTRIAL A N D ENGINEERING CHE&fIfJTRY
1130
All the fractions taken ran less than 1800 grams; therefore the separations, especially in the 12-plate column with the high reflux ratio, are very much worse than would be obtained under truly continuous conditions of operation. For this reason, the curves obtained cannot be considered as more than qualitative and a comparison of Curves V and VI in Fig; 7 is misleading. The amount of pentanes in Fractions 111, V, and VI was determined by careful fractionation in a special laboratory column. The results for Fractions I11 and V in comparison with the range obtained in the regular Engler distillation are plotted in Fig. 8. In all the distillations there was a loss due to not condensing some of the vapors. Cooling with liquid air would have been necessary to make the recoveries strictly quantitative, and this was not available. The losses in the Engler distillations were distributed. Those in the special column were neglected. For that reason, the curves in Fig. 8 do not line up exactly. COMPARISON OF OBSERVED AND CALCULATED RESULTS The amounts of pentanes which should be in fractions of hexane and higher oils cut between 60' and 70" C. under different conditions were calculated approximately. These amounts with those actually found are given in Table 111. (The H. E. T. P. is taken as two actual plates.) TABLE 111-AMOUNT OF No. actual
PENTANE I N A
plates in column
H
4 12 12
2
5 5
60'
TO
-PER CENT Caldulated
70'
c. CUT O F GASOLINE
PENTANB-
2.5 8.0 2
Found
19 15 9.5
Vol. 16, No. 11
There are several explanations for the large discrepancies between the amounts calculated and found. The calculation was made for a single hexane boiling at 6.5' C. The presence of others boiling around 60' C. would make a difference. Moreover, as mentioned before, the hold-up on the plates of' the column would introduce a serious error. Unfortunately, there was not time to clear up these points. A comparison of Curves I1 and V is shown in Fig. 9. Evidently there is a considerable gain in sharpness of cut in increasing the efficiency of the column 200 per cent. However, the difference cannot be directly correlated with the theory as was done in the case of the mixtures of acetone and methanol. The data only indicate the results that may be obtained by experiments made under the proper conditions. CONCLUSIONS
It is safe to say that many of the scrubbers or fractionating columns now in use in petroleum refineries are not so efficient as they should be. The most economical installation for any given separation can probably be most easily determined by experiments similar to those described. These experiments would, of course, include checking up and calibrating the small columns used and also the plant columns by the theory outlined. Comparatively simple tests would show approximately the heat expenditure needed and the efficiency of the column required to make certain rough cuts. The accurate determination of the economical balance between heat consumption, column efficiency, and sharpness of cut for each product is a more complex problem, but one for which a definite solution can be worked out.
Notes on the Preparation of Standard Cellulose-II'~z By A. B. Corey and H.LeB. Gray EASTMAN KODAKCo., ROCHESTER, N. Y.
I N A previous paper3 it was noted that the standard cellulose prepared by the tentative method described, gave too high an ash. It has been found that if the resulting cellulose, before drying, is treated with 1 per cent acetic acid solution for 2 hours a t room temperature and then washed with four changes of distilled water, the ash content is reduced to a very low quantity without any apparent injurious effect on the cellulose. Table I gives results obtained on two different samples. In each case the cellulose prepared as previously recommended was divided into two portions and one of them treated with acetic acid as described above.
The writers have observed, during the alkali boiling of different cottons, that with some a longer time is necessary to discharge the yellow color of the solution than with others. Table I1 shows that the percentage of a-cellulose may b e slightly increased by boiling with the 1 per cent sodium hydroxide solution for 10 hours instead of 6. It seems advisable to allow the displacing alkali solution to enter a little more rapidly' so that 12 liters are used during the time of boiling; and also to continue the heating and displacement with 1 per cent alkali for 1 hour after the yellow color has entirely disappeared. TABLE11
TABLE I
Wan namaker's Cleveland
Without acid treatment
American Peeler (Combed sliver)
Without acid treatment
With acetic acid treatment
With acetic acid treatment
Moisture Ash a-Cellulose Per Per Per cent cent cent 0.12 99.66
0.13 0.06 0.02 0.11 0.11 0.03 0.04
99.71 99.85 99.71 99.61 99.74 99.54 99.76
Received September 24, 1924. Communication No. 216 from the Research Laboratory of the Eastman Kodak Company. 8 THIS J O U R N A L , 16, 853 (1924). 1 2
6 hours' alkali treatment and acetic acid treatment 10 hours' alkali treatment and acetic acid treatment
Moisture Ash u-Cellulose Per Per Per cent cent cent 0.06 99.69
0.00
{ ;: E
0.07
0.04 0.04
99.48 99.48 g9.S4 99.85
The apparatus used by the writers is the she recommended: by the A. C. S. committee4and 76 grams of cellulose are used instead of 100 grams. The corrected capper numbers of the cottons, while relatively low, are not recorded in the accompanying tables on account of the erratic results obtained, which are apparently due to errars in the method oE determination as given by the committee. 4
THISJOURNAL, lS, 748 (1923).
