INDUSTRIAL A N D ENGINEERING CHEMISTRY
162
the sample either by flowing on top for the production of a blue zone or by mixing with the milk-treated reagent. This gives the uniform blue color which is due to the presence of small amounts of hydrogen peroxide. The vanadic acid test is worthless for this purpose, since controls of cocoa and sugar alone give it very distinctly. Slight but distinct positive tests are also given by the latter by the zone method, using benzidine and p-phenylenediamine, but on mixing no trace of blue color is observable. Based upon a large number of tests made during the past summer, the authors have found that while the starch iodide method, applied as above directed, affords no blue tint on controls by either modification of the procedure, it does produce a decided color in the mixture in the presence of traces of added hydrogen peroxide. For this purpose, there-
Vol. 19, No. 1
fore, it is believed that this is the best test and that it is entirely reliable. Every sample of chocolate soda, based upon the cold process and known to have been prepared with hydrogen peroxide, examined by the authors gave positive tests by the starch iodide method for considerable periods after manufacture. In all, about two dozen samples were examined. The longest time any of these samples was held under observation was approximately three weeks, and none showed complete disappearance of this compound. In addition to the control referred to, entirely negative tests have been afforded by all chocolate sodas based upon the use of sodium benzoate alone as a preservative. Our findings in this respect are corroborative of those of F. N. Boyles.3 8
Nal. Bottlers' Curette, 106 (September, 1926).
Effect of Temperature upon Freeness of By D. S. Davis BUREAUOF TESTS,INTERNATIONAL PAPERCo., GLENSFALLS,N. Y
F kww;;:ag;;:
REENESS, aa applied
Plots are given which show the effect of temperature upon the freeness (rate of drainage) of sulfite stocks. The effect is accounted for almost entirely by the viscosity of the suspending medium. Plots are also included, showing freeness as a function of viscosity, the rate of change of freeness with temperature as a function of temperature and the amount of steam required to free a stock as a function of its initial freeness. To assist in the study of the rate of change of freeness with temperature, the freeness-temperature data have been subjected to a simple, general mathematical treatment. Data herein given show that the freeness-consistency chart of a previous paper, intended for use at 20° C., is applicable a t other temperatures between consistencies of 0.35 and 0.45 per cent. It is shown that sulfite stock acquires no "permanent set" in freeness upon heating, thus strengthening the viscosity theory. Data are included which show the extent to which a sulfite stock becomes slower upon standing.
rate of drainage of water from the fibers and is closely related to the characteristics of the paper and to the operation of the machine. Considering sulfite stock alone, two factors, in addition to the action of the beaters and jordans, influence freeness. These are the consistency of the fiber suspension and the temperature of the stock. The effect of increasing consistency is to decrease the freeness of a given stock, for, as the fiber content of a unit volume increases, a thicker mat is deposited u p o n t h e Fourdriniei wire and this mat offers greater resistance to the flow of water. In a previous paperZthe author has shown that in the case of the Model "B" Williams Freeness Tester the reciprocal of the freeness is a linear function of the consistency of sulfite stock. The effect of temperature upon freeness is of interest because of the non-uniformity of temperature of the stock as it leaves the machine chest on the way to the wire. During the beating of the stock, which may take from 1 to 4 hours, depending upon the demand of the machine, the temperature rise may vary from 10' to 20' C. Still greater temperature rises may occur during the passage of the stock through the jordans and the temperature of broke a t the time of the dumping of the broke beaters is often as high as 40" C. Temperature variation may be seasonal as well, for sulfite furnished to the beaters may be at a temperature of less than 10" C. in the winter and as high as 25' C . , in the summer. While it is true that much of the variation is taken up in the beater and machine chests, the temperature of the stock a t the head 1 2
Received July 8, 1926. T m s JOURNAL, IS, 631 (1926).
box of the machine is by no means constant. Further variations occur during dilution of the stock before passage to the wire, depending upon the relative amounts of white water and fresh water used. Concerning the effect of temperature upon freeness, Cline3 wrote:
The importance of temperature as a factor in (freeness) testing is shown by the curve*** which indicates how rapidly the rate of flow varies with changes in the temperature of the water; this shows diagrammatically the viscosity variation of the water with temperature. It is very evident that the less viscous a fluid is the more easily it will pass through a filtering medium.
This has also been brought out by Smith.4 Little experimental work has been done upon the effect of temperature, notably that of M o n r ~ e . With ~ a tester similar to the Green type, he determined the variation of freeness of groundwood between 40" and 90" F. but did not attempt to tie up the data with viscosity or to explain the effect in any other way. It is the purpose of the present paper to show the effect of temperature upon the freeness of sulfite stocks, using the Model "B" Williams Freeness Tester described previously.2 Experimental Method
FREENESS OF WATER-TO make sure that the freeness of a given stock depends upon the mechanism of the drainage of the water through the fiber mat and is not affected by the resistance offered by the wire, water at 7 " , 20", and 50" C. "The Manufacture of Pulp and Paper," Vol. 111, McGraw-Hill Book Co.,1922. 4 Papier-Fabr., 17, 1121 (1919). I Paper Trade J., 74, 235 (1922).
0 8, p.
35,
INDUSTRIAL A N D ENGINEERING CHEMISTRY
January, 1927
was poured into the cup of the tester and its ‘“freeness” determined. Amounts varying from 100 cc. to 1 liter were used. Table I shows that for water alone the flow is independent of the temperature and viscosity. This would be expected from the design of the freeness tester, which in no way resembles a viscometer. Table I
F
1
= lO0OCC.
V
926 923 923 800 CC. 738 739 737
7.1 19.5 50.0 7.5 19.7 50.0
V 7.4 19.9 53.0
r)
v
v
-
500
1.42 1.02 0.56 1.38 1.01 0.56
CC.
1.40 1.01 0.53
457 457 457
= 100 cc. 1.88 1.00 0.59
75 7s 75
7.5 20.3 46.0
V = Volume in cc. of water added t o cup at viscosity is q centipoises.
1’ C., at which temperature the
F is the “freeness” of the water.
METHODOF TESTIXG STOCK-In contrast to the previous work done with the Williams tester, the only unit of that apparatus used was the tester proper. This change necessi-
163
The cloth and fiber mat were dried to constant weight in an oven a t 105” C. This procedure is much longer, but no less accurate, than that which may be followed with the entire Williams outfit. The stocks mere prepared by beating unbleached sulfite in a small experimental beater, varying the time of beating to change the freeness. The stock was transferred to the tub and made up to 0.40 =t 0.01 per cent consistency. Nine 1 - l i t e r samples /o were tested a t temperatures between 5Oand5O0C. The freeness tester was brought to the desired temperature 7 before each run by 6 p o u r i n g warmed o r cooled water 2 through it. After 8 5 a little practice,; + considerable technic in adjusting the temperature was 3 easily acquired, so that the temperatures of the water j u s t before a n d ’ just after passage through the wire Oo 20 30 10 50 60 TfMPtRATURf t Z. checked within a Figure 2 few tenths of a degree. Correction was made for the expansion or contraction of the water from the temperature of the tub to that of the run. Freeness values, determined between 0.39 and 0.41 per cent, were corrected to the standard 0.400 per cent by use of Figure 5 of the previous paper. Results
34
d‘
I 20
B
TC#PfRA TURC,
A io
6L
t ‘c.
Figure 1
tated an alteration in experimental procedure, as did also the fact that 9 liters of stock were necessary for a single run. While it was quite possible to agitate 6 or 8 liters of 0.4 per cent stock in a pail with the motor-driven stirrer and to have successive liter samples dipped from the pail agree closely in fiber content, the agreement became poorer as the volume of stock remaining decreased. Also, the small stirrer was hardly sufficient to stir uniformly an amount much larger than 8 or 10 liters. Fifty liters of stock were made up in a tub and stirred by hand, and liter samples were withdrawn. With hand stirring, however, successive samples did not agree closely enough and it was necessary to determine the fiber content of every sample poured through the tester. This was done by removing the stock from the cup after each determination, combining it with the water from the two orifices, and filtering the mixture through a dried and weighed cloth.
T’ARIATION WITH TEMPERATURE-Figure 1 shows the variation of freeness with temperature for four sulfite stocks covering a wide range. Run 1 represented a stock somewhat more free than would correspond to sulfite as furnished to the beaters in actual practice, while run 6 was made with one the freeness of which was about that of well-beaten stock. It will be seen that the general shapes of all four curves are the same, indicating that equations of the same type may be used to connect the variables. I n every case the rate of change of freeness with temperature drops off with increasing temperature, each curve apparently approaching an asymptote. This suggests that the rate of change of freeness is proportional a t all times to the difference between the freeness and the asymptote of the curve, that is, that
where F = freeness t = temperature, ’ C . 4 = freeness asymptote
Rearranging the expression for integration, it becomes -= dF
Kdt
d - F
Integrating, --In ( 4
- F)
=
Kt
+c + c)
where c is the constant of integration, or In (+
- F)
=
-(Kt
Using the exponential form, this becomes + - F = e-(Kt+e) where e is the base of natural logarithms, from which F = + - e-(Kt+c)
IlVD L’STRIAL AND ENGINEERING CHEMISTRY
164
VOl. 19, No. 1 Table I1
The equations of the curves are
F,
Run
F = 776 F = 646 F = 716
4 6
7
It is evident from Figure 1 that freeness changes more rapidly with temperature in the case of a slow stock than in the case of a free stock. Figure 2 is a plot of the rate of change of freeness with temperature against temperature. The ordinate is the rate of change of freeness and is calculated from the expression, dt
= K(C
- F)
The equations for rate of change for these runs are: Run 1 4 6 7
- F) $ = 0.0205(776 - F) dF dt = 0.0283(646 - F) d- F= dt
at
F, a t t.
F, at
7.
- e - 0 ‘ Q 2 0 0 j t + 6.168 - e - 0 . 0 2 8 W 4- 6.178 - e-0.05621 4- 5.416
0.0211(812
= 0.0552(716
-
F)
VARIATION WITH VIsCosITY-Figure 3 shows the variation of freeness of these stocks with the viscosity of water at the temperature a t which the tests were made. The forms of the curves are similar, but it will be noted that run 7 gave rise to a curve which is concave to the direction to which the others are convex. Run 7 was s o m e w h a t irregular in Figure 1 also. The question arises: Which factor influences freeness, temperature or Viscosity? That is, does temperature affect freeness because of its influence upon the viscosity of the suspending medium or for other reasons as well? The matter was settled in the following way: The freeness, F1, of a stockwas determined a t tl’ C., a t which the viscosity of water was vl W S C 0 5 f T ~I “/O CF#T/PO/XS centipoises. The stock Figure 3 was filtered t h r o u g h a cloth, excess water was removed by suction, and the damp fibers were suspended in a liter of 20 per cent sugar solution. The freeness, F z ,was again determined, the viscosity remaining vl, but the temperature being different, tz. Should F1 and F z be equal it would indicate that temperature affected freeness only by virtue of the resulting change in viscosity or, stated differently, that suspending media of equal viscosities give rise to equal freeness values regardless of the temperatures involved. On the other hand, if FI did not equal F1 but did equal the freeness of the stock suspended in water alone a t t a o C., it would show that not the viscosity effect of temperature, but some other temperature effect, influenced freeness. Table I1 gives data found with stocks of runs 4, 6, and 7 , which settle this point nicely. Twenty per cent sugar solutions were used and correction in concentration was made for the water remaining in the damp fibers after filtration.
P a = Freeness determined in a sugar solution the temperature of which is t s and the viscosity of which is qa. F, denotes freeness determined in water suspension.
In every case it was found that the freeness 30 values determined with the sugar solution a t viscosities of a b o u t 1.19 centipoises and tempera- 8 tures of approximately h‘ 40’ C. were only a trifle $ zo higher than those determined with water a t the ,J s a m e viscosity but a t 2 about 13.5’ C. B The discrepancies between the values found os in the sugar solution and those obtained in water at the same viscosity
SrJ ~
3
perimental error. That is, some other, comparatively slight, temperature effect beside viscosity must be in operation. These data bear out very well the statement of Smith:6 The rate of drainage may, however, sometimes be increased in still greater proportion than that in which the viscosity of the water is increased.’ Such additional increase in drainage is Erobably due t o the fact t h a t on heating the fibers become dehydrated,” shrink, and become thinner. This causes the interstices between the fibers t o become larger, and since they represent capillaries, the water is able t o drain away more rapidly than it would if the size of the fibers remained unchanged.
T h e d a t a for the viscosities of sugar solutions of various concentrations and tern- 5 peratures plotted $ in Figure 4 are those of Bingham and Jacksons and 8 \ of Herschel.0
4
’
3
Y 2 TEMPERATURE VARIATIONS FOR Q
B
FREENESS-CONSISTENCY CHARTY -The freenessconsistency chart given in the previous paper was intended for use
5
I
/I
“The Action of the Beater,” B. T.Batsford, Ltd., London, 1923. From the context immediately preceding this statement i t is evident t h a t the word is meant to be “decreased.” The error probably crept in during the translation from Dr. Smith’s original Danish dissertation, “Heltojshollaenderen. ” 8 B u r . Standards, sci. Paper 298 (1917). 0 B u r . Standards, Tech. Paper 100 (1917). 6
7
165
INDUSTRIAL A N D ESGINEERING CHEMISTRY
January, 1927
It may, however, be used at other temperatures bet,n-een consistencies of 0.35 and 0.45 per cent with a fair degree of accuracy. Table I11 includes data bearing out this statement. Freeness determinations were made on the stock of run 4 a t temperatures between 11" and 40" C. and consistencies of about 0.31 per cent. The values obtained were converted to the standard 0.400 per cent consistency by use oE the chart and compared with values determined a t consistencies much closer to 0.400 per cent (0.401 to 0.415 per cent). corrected to 0.400 per cent by the same chart.
SLOW~SG OF SrocK-Sulfite stock becomes somewhat slower upon standing, owing, doubtless, to a slight fiber decomposition. The stocks of runs 1 and 6 were allowed to stand a t a consistency of 0.4 per cent and a temperature of about 20" C., for 24 and 30 days, respectively. Table V gives the change in freeness during the intervals for temperatures of 20", 30", and 40" C.
Table 111
Run 1 667 696 718 Run 6
1
10 3 25 7 41.7
c
0,3455 0.3620 0.3385
~
F at C
F at 0.400%
414 528 607
381 499 571
F Run 4)
389 493 574
Table t
1st day
20 30 40
68 1 706 726
20 30 40
373 440 491
V
F 24th day
... ... ...
30th day
Change
... ... ...
14 10 8
340 403 461
33 37 30
PERMANEST SET-It was desired to determine whether STEAJINEEDEDTO FREEA STOCK-It is common practice or not there was any temperature lag or "permanent set" of freeness acquired by a stock. The freeness of a sample of machine tenders to free stock by blowing steam into it of stock of run 4 was determined a t 44" C. Then the sample when it is too slow. With the aid of Figure 1 it is possible was removed from the tester, mixed thoroughly, cooled to 10" to calculate the amount of steam necessary to free a stock of C., and tested again. If no lag or "permanent set" was ac- given freeness and temperature. Figure 5 shows the amount quired, the second determination should agree with the freeness of 50-pound steam (35.3-pound gage) required to free the a t 10" C. read from Figure 1. Once more the values check stock of run 4 through four intervals of 50 freeness units (Table IV), showing no lag or set, and thereby strengthening each, starting at 370 and 8" C., and ending at 620 and 55" C. the conclusion that viscosity influences freeness to a greater A heat loss of 25 per cent was assumed and the calculation was made for steam blown directly into a 0.4 per cent suspension extent than any other factor. of sulfite. Actually the consistency would be somewhat Table IV higher and a part of the dilution and heating would arise t F F ( R u n 4) from the use of warm white mater. However, the plot serves to show how rapidly the steam consumption increases with 44.3 588 ... 10.1 385 387 increasing freeness and temperature of stock.
Rapid Determination of Silicon in 8 to 17 Per Cent Ferrosilicons' By George T. Dougherty AMERICW STEEL FOUNDRIES, CHICAGO, ILL.
HE following grades of
The degree of decomposition of 8 to 17 per cent ferroelectrometallurgical i n d u ssilicons was determined by a new method and also by ferrosilicon are obtaintry, is used for the same purexisting English methods. able on the m a r k e t : pose as Bessemer ferrosilicon, Experiments showed that 10 parts of nitric acid and S i l v e r y pig iron and nonIt has the advantage of in90 parts of hydrochloric acid is the only correct ratio for Bessemer; Bessemer; 14 to 17 troducing less carbon into the complete decomposition of 10 to 17 per cent ferroper cent; 50 per cent; 75 per steel. Fifty per cent ferrosilisilicons. The acids and the ferrosilicon are boiled for cent; and 90 to 98 per cent. con is v e r y generally em1 hour. The composition of the undecomposed mateSilvery pig iron (7 to 9 per ployed in the manufacture of rial left when nitric acid and hydrochloric acid in the cent Si) and non-Bessemer steel. When it is used only other ratios heretofore taken for 14 to 17 per cent ferroferrosilicon (up to 11 or 12 per t r a c e s of c a r b o n need be silicons are used is considered. cent Si) are products of the added. It melts readily into Silicon carbide, suggested by Ibbotson, was not found blast furnace. Because of the steel, even when added in the sample examined. A quick accurate method for t h e i r h i g h phosphorus cond i r e c t l y into the ladle, althe determination of silicon, which is as efficient as the tent, they are used only in though it is infusible if heated standard, but slow, fusion method, has been devised. gray-iron foundries, for addialone. It is composed of tion to the c h a r g e i n t h e about equal parts of silicon cupola to soften the cast iron. Bessemer ferrosilicon (9 to and iron, with less than '/2 of 1 per cent of foreign matter. 12 per cent silicon) was formerly produced only in the blast Heretofore, 75 and 90 to 98 per cent ferrosilicons have been furnace, but it has been made in electric furnaces where employed only on a small scale, probably on account of water power is plentiful. It is used almost exclusively in their low specific gravity. Increasing quantities are now steel works and foundries for deoxidizing and leaving the de- going into high-silicon sheet steel designed for high magnetic sired quantity of silicon in steel to be tapped out. It has the permeability and electric resistance, and lo\\- hysteresis in "Bessemer" limit of 0.1 per cent phosphorus. Fourteen to motors, generators, transformers, and other electrical appaseventeen per cent ferrosilicon, recently introduced by the ratus and for automobile springs. The 97 to 98 per cent 1 Received July 1, 1926. ferrosilicon also has a wide application in nonferrous metal-
T
