INDUSTRIAL AND ENGINEERING CHEMISTRY
212
Results obtained by the modified Parr method were all well within A. S. T. M. tolerances for duplicates in the samelaboratory. With the exception of results on one sample ( 5 ) , the checks between the two laboratories were within A. S. T. M. tolerances. The determination of ash by Method D gives duplicates checking within the 0.3 per cent tolerance for all samples. The adequate removal of sulfur trioxide from the furnace during ashing is important. As compared to results obtained by the modified Parr procedure, Methods A and E gave results within the A. S. T. M. 0.3 per cent tolerance for samples containing up to 0.6 per cent of carbon dioxide; Method B for coals up to 3.6 per cent of carbon dioxide; Method F for coals up to 4.2 per cent of carbon dioxide (with one exception); and Method D for coals containing up t o 3.6 per cent of carbon dioxide. Sulfur trioside-free ash values were similar for all methods. The slow heating method starting with a cold furnace appears to be satisfactory for determining ash in commercial samples of coal containing unusually large amounts of calcite and pyrite.
Vol. 14, No. 3
Methods B, D, and F give most consistent results, with Method D apparently giving the best results of the three. Methods C and G appear to give good results, especially for coals high in calcite and pyrite where other procedures studied are not so satisfactory. This procedure requires more work than other procedures. Adequate removal of sulfur trioxide from the furnace in which ashing takes place is necessary.
Literature Cited S.T. M.Standards, Part 111,Designation D 271-37, pp. 15-16 (1939). Ibid., pp. 20-1 (1939). Ibid., p. 21 (1939). Ibid., p. 41 (1939). Parr, S.W., Coal Mining Investigations, Ill. State Geol. Survey, Bull. 3, 35 (1916). Rees, 0. W., IND.ENG.CHEM.,ANAL.ED.,9, 307-9 (1937). Stanton, F. M., Fieldner, A. C., and Selvig, W. A., U. S.Bur. Mines, Tech. Paper 8, (1938). U. S.Steel Corp. Chemists, “Methods for Sampling and Analysis of Coal, Coke, and By-Products”, 3rd ed., p. 84, 1929.
(1) A. (2) (3) (4) (5)
(6) (7) (8)
Conclusions Methods A and E are not recommended for deterrnining ash in coals high in calcite and pyrite, hecause too much sulfur is retained in the ashes.
PRESENTED before t h e Division of Gas a n d Fuel Chemistry a t the 102nd Meeting of the AMERICANCHQXICALSOCIETY,Atlantio City, N. J. Published by permission of the Chief, Illinois State Geological Survey, and the Director, Bureau of Mines, U. S. Department of the Interior.
Measurement of Color and Turbidity
in Solutions of White Granulated Sugars E. E. MORSE AND R. A. MCGINNIS, Spreckels Sugar Company, Woodland, Calif.
and
A practical method for the measurement of color and turbidity in solutions of granulated sugars is presented, a modification of the method of Keane and Brice. The two assumptions on which their method is based are shown to be not entirely justified. Color measurements with the new method are free from the influence of turbidity, and vice versa.
Tr
Tr =
,Mathematical Relationships The transmittancy of a turbidity-free sugar solution will be represented by T , and that of a colorless sugar solution by Tt. For a solution containing both color and turbidity, the transmittancy, T , is given by the fundamental expression
T , X Tt
(4)
Trt
and set the turbidity index equal to the per cent absorbency of red light:
STRONG need for an adequate method for the measurement of color and turbidity in white granulated sugar solutions has been felt for some time. The best practical method has been that of Keane and Brice ( 2 ) , which as presented, however, has suffered from certain errors arising from the basic assumptions made.
=
(3)
The notation is obvious. Keane and Brice assume that T,,is constant and equal to 1.00 for solutions of white sugars, stating that there is virtually no light absorption in the red part of the spectrum by the small amount of coloring matter present. From this assumption and Equation 3 they obtain
A
T
Tm X Trt
(1)
If the transmittancy measurements are made with light passed by different filters, say a blue-green and a red filter, then To Tgc X Tor (2)
It = l O O ( 1
- Trt) =
lOO(1
- T,)
(5)
They also set the ratio T,t/T,t equal to 1.00, although they state that it is only an approximation. Then from Equations 2 and 3, they obtain
Ta/Tp = Tp/Tm X T,x/T,t
=
T d l X 1 = Tu,
(6)
The color index is thus taken as the per cent absorbency of the blue-green light in a turbidity-free solution and by the assumptions above is expressed as I , = l O O ( 1 - Toe) = lOO(1 - Tg/Tr) (7) Sees (3) was not able to substantiate the assumption of Keane and Brice that both T,, and Tat/T,t equal 1.00. Nees suggested that experimentally determined factors be applied to correct the difficulty and proposed expressing color and turbidity in terms of percentage absorption of blue light. Sees’ method is not satisfactory, in that the use of an additive
ANALYTICAL EDITION
March 15, 1942
213
Experimental Procedure TABLE I. Sugar Sample 1
TRAXSMITTANCIES O F
Run
T7C
1
0.954 0.949 0.950
0.786 0.786 0.783
1 2 . 1 2 1 2
0.890 0.888 0.875 0.875 0.852
1 2
0,884 0.877 0,886
0.769 0.764 0.669 0.676 0.625 0.637 0.731 0.723 0.723
2 3
2 3 4
FILTERED SOLUTIONS
0.855
3
TOC
relationship of the absorbencies due to color and turbidity cannot be employed if a long cell is used. If A is the absorbency, from Equation 1 1 - A = (1
- A,)(1 - At)
(8)
whence
If the absorbencies are low-as was the case with the short cell used by Nees-the term A,At can be neglected. However, if a long cell is used and the absorbencies vary from roughly 0.15 to 0.50, the term A,A, cannot be neglected. The absorbencies obtained with a cell of the length used by Nees are not large enough to permit adequate photometric accuracy to be obtained (6). It would seem that the best solution t o the problem is to determine experimentally the relationships between T,, and Toeand between T,,and Tgf. By means of these relationships and Equations 2 and 3, the color and turbidity indices can be calculated and expressed as I,
=
lOO(1
It = l O O ( 1
-
!roc)
- T,t)
The primary transmission standard used in this work was a colorless, turbidity-free 50 refractometer dry substance (R. D. S.) sugar solution. It was prepared from confectioners' sanding sugar by adding Darco decolorizing carbon to the hot solution, allowing it to cool, filtering on a Buchner funnel through No. 40 Whatman paper, and filtering through asbestos according to the recommendations of Peters and Phelps (4). In this work "turbidity-free" is applied to any solution which was filtered through the specially prepared asbestos. There has been much discussion in the literature regarding color adsorption of asbestos and other filtering media (1, 4, 6). However, experiments made by the authors indicate that any adsorption of coloring matter from solutions of granulated sugar by asbestos is slight and can be neglected without introducing serious error. For convenience, a secondary transmission standard was prepared and standardized against the primary standard. Two 5cm. squares of thin glass from photographic plates were bound together ~ i t the h inner surfaces separated by a border mask of thin cardboard. The transmittancies of this absorber for red light and blue-green light were determined, taking the transmittancy of the standard sugar solution in the 25-cm. absorption cell as 1.000 in each case. The secondary standard was checked in this manner several times during the course of the work. In routine runs, the circuit of the Lumetron was readily balanced by using the secondary standard without the necessity of having standard sugar solutions always on hand. Solutions of granulated sugar (50 R. D. S.) were prepared by mixing equal weights of sugar and boiling double-distilled water. After cooling to room temperature, the transmittancies of the solutions were measured in the 25-cm. cell using first the bluegreen and then the red filter. The solutions were next filtered through asbestos and the transmittancies again determined. Duplicate and triplicate runs made with several sugar samples shorn that the transmittancies of the asbestoq-filtered solutions are reproducible (Table I).
(10)
A considerable number of colorless but turbid 50 R. D. S. sugar solutions were also run in the colorimeter. The turbidizing agent was prepared by adding a little fuller's earth to a colorless sugar solution, stirring well, and allowing t o settle overnight. The supernatant liquid was decanted and used to turbidize other colorless sugar solutions. A few measurements were carried out on solutions made turbid with finely divided amorphous sulfur.
(11)
Transmittancy Measurements
Thus the indices are expressed by equations of the same form as employed by Keane and Brice.
Table I1 contains the results of the transmittancy measurements made before and after filtration. .4 large number of
Description of Apparatus A Lumetron photoelectric colorimeter, Model 402E, manufactured by the Photovolt Corporation, New York, N. Y., was used for the transmittancy measurements. The instrument was altered to take a 25-cm. cell and the light source was replaced by a 6- to 8-volt, single-filament automobile headlamp which was lighted by storage batteries. The two filters used were the same as employed by Keane and Brice (Corning light shade blue-green, NO. 428, 3.4 mm. thick, and Corning traffic red, No. 245, 3.05 mm. thick. The No. 428 filter used in this work was from melt 194). Data supplied by the manufacturer indicate that the transmission curves for the No. 428 filter are practically identiial for different melts of lass. The No. 245 filter covers a narrower spectral range and shodd be readily reproducible. If necessary, slight adjustments in filter thickness can be made to correct for any difference in the melts. The color temperature of the light source was arbitrarily set at 2485' Kelvin. It was measured with an Eastman color temperature meter. For convenience in routine work, the lamp temperature adjustment is made by noting the galvanometer deflection with the So. 428 filter in position. This was checked from time to time against the Eastman meter. Experiments showed that the measured transmittancies were not dependent to any marked extent on the color temperature of the lamp. A change of 160' in the temperature did not change the measured transmittancy with the red filter a measurable amount and changed the blue filter reading 1.9 per cent. The color temperature can probably be adjusted to nithin IS", which is equivalent to a transmittancy variation of 0.2 per cent.
-
1.10
LOB'
,%.
LEGEND,OSULFUR oFULLER'S EARTH
104-
-
1.02
a = 1.224- 0 . 2 2 0 T p t Tsl
Trt
FIGURE 1.
RELATIONSHIP F O R TURBID BUT COLORLESS SUGAR SOLUTIONS
TRANSMKTTANCY
Vol. 14, No. 3
INDUSTRIAL AND ENGINEERING CHEMISTRY
214
samples of beet sugar from three beet factories and a lesser number of cane samples from a cane sugar refinery were used in the work. All the beet sugar samples were of white granulated sugar. The cane sugar samples were of varieties designated in Table 11. I n a number of cases transmittancy measurements were not made before filtration of the solutions through asbestos. The ratio Tr,/Tgtwas calculated from the relationship Trt/Tgt =
zC
T To, 7; X
The results of the measurements on the turbid but colorless sugar solutions are given in Table 111. RELATIONSHIPS BETWEEN T,, AND T,t. The data in Tables I1 and I11 show plainly that T,t/T,t cannot be set equal to 1.00 if accuracy is desired. I n cases of high turbidity the ratio departs markedly from 1-00,as is shown with samples 18, 20, and 32 from Factory 1, where the ratio is about 1.2. It is therefore necessary to establish from the experimental data the relationship between T,t and Tut. This relationship can be obtained from the data in Table 11, but it is more advantageous to use the data in Table I11 which were obtained directly with artificial turbidity in colorless sugar solutions. I n the first place, the use of artificial turbidity allows one to cover a greater range of turbidity and with greater uniformity. Secondly, i t permits the use of a more nearly true turbidity rather than having to depend upon chance in using natural sugar turbidity. Often the low transmittancies observed with sugar solutions are due t o fibers, large dust particles, and the like, especially if the samples have been stored in cloth bags. Even what might be called true turbidity is not constant in nature or particle size, but depends on its source and other factors. It was found empirically that the relationship between T,-tand Tot is best expressed by kzTr1. a n equation of the form T,t/T,, = kl The data in Table I11 were treated by the method of least squares and the equation obtained was
+
T,t/T,t = 1.224
- 0.220Trt
TABLE11. TRANSMITTANCIES Sugar Sample
TJTr
Toc/Tio
Toe - 3 Tic TI
Beet Sugar Factory A 1 2 3 4 '
5
6
7
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
.... .... .... ....
.... ....
.... .... ....
.... .... ....
....
.... .... .... . . . . .... 0.807 0.680 0.807 0.672 0.722 0.630 0.726 0.811 0.601 0,687 0.461 0.803 0.776 0.618 0.742 0.766 0.821 0.680 0.671 0.887 0.724 0.482 0.803 0.798 0.563 0.541
0.632 0.463 0.637 0.486 0.527 0.437 0.561 0.600 0.383 0.517 0.284 0.603 0.599 0.427 0,552 0.572 0.654 0.482 0.466 0.669 0.532 0.292 0.602 0.605 0.419 0.406
0.888 0.889 0.893 0.916 0,924 0.937 0.906 0.880 0.926 0.925 0.901 0.931 0.911 0.897 0.874 0.912 0,909 0.876 0.854 0.852 0.896 0.909 0.876 0.89? 0.917 0.909 0.888
0.855
0.928 0.897 0.852 0.911 0.912 0.900 0.889
0.688 0.703 0.682 0.720 0.775 0.775 0.704 0.661 0.771 0.759 0.670 0.752 0.730 0.693 0.669 0.735 0.697 0.678 0.612 0.625 0.711 0.719 0.684 0.719 0.721 0.733 0.689 0.649 0.748 0.698 0.651 0.718 0.730 0.701 0.702
.... .... .... .... .... .... .... .... .... 0.783
0.775 0.791 0.764 0.786 0.839 0.827 0.777 0.751 0.833 0.821 0.744 0.808 0.801 0.773 0.765 0.806 0.767 0.774 0.717 0.734 0.794 0.791 0.781 0.802 0.786 0.806 0.776 0.759 0.806 0.778 0.764 0.788 0.800 0.779 0.790
0.684 0.789 0.723 0.730 0.694 0.773 0.740 0.637 0.753 0.616 0.751 0.772 0.691 0.744 0.747 0.797 0.709 0.694 0.781 0.735 0.606 0.750 0.758 0.744 0.750
.... ....
.... .... .
.
I
.
.... .
.
I
.
.... ....
0.038 0.060 0.019
0.078
0.043 0.071 0.033 0.027 0.137 -0.036 0.118 0.043 0.019 0.090 0.058 0.039 0.009 0.067 0.065 0.025 0.043 0.15s 0.038 0.042 0.035 0.040
Trt/Tg
... ... ... ... ... ... ...
...
...
1.05 1.09 1.02 1.11 1.06 1.10 1.04 1.04 1.22 0.95 1.19 1.06 1.03 1.13 1.08 1.05 1.01 1.09 1.09 1.03 1.06 1.26 1.05 1.06 1.05
1.05
Beet Sugar Factory B 1 2 3 4 5 6 7 S 9 10 11 12 13 14 1. i 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
(12)
The average difference between the observed and calculated values of T,t/Tgtis 0.008. The data have been plotted in Figure 1, RELATIONSHIP BETWEEN T,, AND Toe. Early in this work i t was realized by the authors that colored but turbidity-free solutions did not transmit all the light passed by the red (Corning No. 245) filter. It was a t first thought that possibly some constant value of T,,could be employed, but such did not prove to be the case. An analysis of the data in Table 11 showed that the relationship between T,, and Trocould be well expressed by an equation of the same type as was used for the turbidity ratio-namely, To, = k3 k4 Tot. This relationship was obtained using only the data for the beet sugar samples, inasmuch as it was found that no significant difference was obtained between the equations for the individual beet plants, but that they did differ considerably from
+
Transmittancies Before After Filtration Filtration TI To Tic Too
0.693
.... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... ....
....
.... .... .... .... ....
.... ....
....
0.833
.... ....
....
0.799 0.804 0.813 0.841 0,838 0.890
0.106
1.15
0.883 0.864 0.864 0.821 0.880 0.821 0.829 0.856 0. SO6 0.861 0.849 0.832 0.829 0.857 0,857 0.854 0.757 0.827 0.806 0.843 0.860 0,836 0.849 0.804
.... .... .... ....
.... .... .... .... ....
... ... .. .. .. ...
0.898
.... ....
.... .... ....
.... .... .... .... .... ....
.... ....
.... .... .... ....
0.027
....
.... ....
... ...
...
.. .. .. ... ... ... ... ... ... ... ... ... ...
... ... ... ... ... ...
1.03
... ... ...
the equation obtained for the cane sugar samples. Thus i t seems advisable to use one set of coefficients for beet sugar and one set for cane sugar. Most of the samples investigated in this work were beet sugar samples (107 beet, 16 cane) and the equation presented applies to beet sugar. Many more cane samples should be run to obtain a truly representative equation for cane sugar. The final equation obtained for beet sugar was T,,/T,, = 0.310
+ 0.673Tuc
(13)
and the average difference between the observed and calculated values of the ratio is 0.007.
Derivation of Equations for Color and Turbidity Indices If the color of a sugar solution is to be expressed as the per cent absorbency of blue-green light by the turbidity-free
OF
VARIOUSSUGARSOLUTIONS Transmittancies Before After Filtration Filtration
Sugar Sample
TI
To
TIC
Toc
2 c
TdTr
TgdTrc
Trc
Beet Sugar Factory B (Cont'd)
32 33
........ ........
0.948 0.940
0.837 0.822
.... ....
-2 TI
....
0.883 0.874
....
Trt/Tgt
... ...
0.764 0.772 0.763 0.767 0.792 0.785 0.794 0.786 0.773 0.762 0.757 0.770 0.734 0.732 0.728 0.743 0.706 0.693 0.695 0.737 0.763 0.753 0.795 0.787 0.798 0.763 0.765 0.760 0.759 0.739 0.756 0.792 0.784 0.754 0.765 0.747 0.696 0,686 0.703
0.821 0.827 0.819 0.813 0.835 0.836 0.836 0.824 0.821 0.819 0.820 0.828
0.800
0.797 0.786
0.806
0.772 0.777 0.772 0.805 0.818 0.811 0.844 0.841 0.842 0.819
0,819
0.823
0.815
0.803 0.824 0.841 0.843 0.818 0.813 0.809 0.776 0.781 0.779
0.011 0.013 0.013 -0.003 0.041 0.006 0.019 -0,004 0.014 0.021 -0.002 0.008 0.007 0.020 0,008 0,016 0.008 0.070 0.010 0.017 0.006 0.002 0.014 0.018 0.012 0.014 0.003 0.037 0.017 0,002 0.006 0.023 0,023 0.020 0.014 0.010 0.035 0.088 0.016
1.01 1.02 1.02 1.00 1.05 1.01 1.02 1.00 1.02 1.03 1.00 1.01 1.01 1.03 1.01 1.02 1.01 1.10 1.01 1.02 1.01 1.00 1.02 1.02 1.01 1.02 1.00 1.05 1.02 1.00 1.01 1.03 1.03 1.03 1.02 1.01 1.05 1.13 1.02
T,t'
.... .... .... ........ .. .. .. ..
h
0.884
0.877
0.886
0.974
0.981 0.975
0.985
0.731 0.723 0.723 0.946
.... .... .... .... .. .. .. .. ....
0.945 0.945 0.962 0.870 0.797 0.717 0.968
0.873 0.828 0.732 0.979
0.827 0.824 0.816 0.971
.... .... .... .... .... .... ....
Comparison of Observed and Calculated Color and Turbidity Indices A practical test of the method can be made by comparing the observed and calculated color and turbidity indices. From the data in Table I1 the color index is given as l O O ( 1 -TOE) and the turbidity index is l O O ( 1 - Tr/TrC). I n Table IV these indices are compared with the indices calculated from Eauations 14 and 15; using the observed values bf Toand Tr. The average difference between the calculated and observed color indices is 1.9 units; for the turbidity indices, it is 1.4 units. The agreement is especially gratifying in the cases of high turbidity.
... ...
...
...
0.031
0.783 0.985
0.051 0.006
0.024
1.04 1.03 1.07 1.01
...
0.7i3 0.703 0.602 0.928
0.962 0.930 0.916 0.983
0.886
0.827
0.967
0.933
0.933
0.965
0.032
1.03
0.920 0.907 0.768 0.772
0.870 0.868 0.624 0.595
0,983 0.985 0.895 0.873
0.938 0.953 0.747 0.718
0.946 0.957 0.813 0.771
0.954
0.008 0,011 0.022
1.01 1.01 1.03 1.07
0.852
0,968
0.835
0.822
0.051
+ T,t[ -5.564 - Tr(0.673 - 1.409/To)] +
Only one root in each equation is significant. Tu,must be greater than or equal to T,, but less than 1.00. Also T,t must be greater than or equal to T,, but less than 1.00. A table was prepared t 5 substituting various values of Toand Tr in Equations 14 and 15 to obtain the transmittancies and then these were converted readily to per cent absorbencies, the units of the color and turbidity indices.
... ...
0.963 0.969 0.977 0,904
+ Toc[0.461 + Tg(0.220 -O.lOITg 1.819/Tr)] + = 0 (14) 3.7441: = 0 (15)
Cane Sugar Factory C a n e granulated . . . . C a n e granulated . . . . C a n e granulated . . . . C a n e cubes Extra hard cubes cubes .. .. .. .. Cocktail Tablets No. 1. wet d.'8S5 S o . 3 wet 0,849 N o . 4 wet 0.822 Wetcube 0.948 Confectioners'
solution, it is necessary to calculate To,from the measured values bf To and Tr, employing Equations 2, 3, 12, and 13. Similarly, the turbidity index can be calculated by h d ing T,t. After performing the algebra the following equations for To, and for T,t are obtained: Toez
Beet Sugar Factory C
Confectioners' AA Sanding Bar Baker's
215
ANALYTICAL EDITION
March 15, 1942
Practical Application
J
The method has been applied for practical control work a t the Woodland factory, and has functioned in a very satis-
TABLE111. TRANSMITTANCIES OF TURBIDSUGARSOLUTIONS T y p e of Turbidity
Sulfur Fuller's earth
Tit
Tot
T d Tor
Type oi Turbidity Fuller's earth (Cont'd)
Trr
TrJTot
216
INDUSTRIAL AND ENGINEERING CHEMISTRY -
1.0
The color temperature of the light source is checked. The blue-green filter and secondary standard are inserted and the Lumetron is balanced to the required value. The secondary standard is removed, the absorption cell inserted, and a reading made of the transmission. The same procedure is carried out with the red filter. From the two readings, the color and turbidity indices are obt a i n e d from tables. (Complete directions and copies of the tables will be furnished at cost to anyone interested.)
LEGEND: 0 CANE SUGAR
.
L
.. .'
.. -
..
..
..
Vol. 14, No. 3
c
.9
35 Trc
Bt
E=0.310+0.673
T*
Discussion The color and turbidity indices in this method are given as per cent absorbencies I I I I .7 3 due to color or tur.70 .8 0 .so 1.00 bidity for a n absorpf9C tion cell 25 cm. in FIGURE 2. TRANSMITTANCY RELATIONSHIPS FOR SUGAR SOLUTIONS CONTAININQ COLORBUT length. Naturally the NOTTURBIDITY values will differ for another cell length. It has been found, howfactory manner. About 7 minutes are required for each comever, that a cell of this length is necessary for optimum abplete analysis. sorption ( 5 ) . With control of the color temperature of the illuminant, One hundred and fifty grams of sugar are dissolved in an equal and some care in duplication of light filters, there should be weight of hot distilled water, and stirred into solution. The little difficulty in obtaining the same results hot solution is poured through a heat exchanger, from which it with different instruments* emerges a t approximately room temperature. The cooled sohI n order to save time, the sugar samples are dissolved in tion is poured into the absorption cell.
TABLE IV. COMPARISON OF OBSERVED AND CALCULATED COLORAND TURBIDITY INDICES Sugar Sample, Factory A 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Color Index Observed Calculated
Turbidity Index Observed Calculated
24 33 25 27 31 33 26 30 32 39 37 29 28 32 28 28 27 31 35 25 30 35 28 27 30 30
27 3s 25 31 32 36 27 34 470 28" 47" 32 28 36 31 33 25 36 36 29 32 48a 32 32 24a 224
13 25 13 26 20 28 20 11 31 20 46 10 15 30 17 17 10 23 22 7.7 19 43 12 13 37 39
24 23 24 23 21 21 21 21
23 23 25 23 25 19 21 22
8.8 7 6 9.2 7.7 12 9 2 9 2 7 2
12 19 12 24 19 27 20 8 25 24 42 10 14 28 17 14 11 21 22 5.4 19 39 10 11
3s 41
Factory C 8.7 7.6 9.0 6.6 10
9.9 8.1 5.7
Sugar Sample, Factory C 9 10 11 12 13 14 15 16 17
1s
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39
Color Index Observed Calculated 24 23 25 24 21 24 22 23 27 27 29 27 29 27 28 26 31 29 37 31 29 30 27 26 23 24 23 25 21 20 21 21 21 20 25 24 22 23 27 24 26 24 25 26 22 24 22 21 21 22 26 25 25 23 25 25 29 30 29 31 31 30
Turbidity Index Observed Calculated 5.4 7.0 8.7 9.5 10 8.3 5.5 5.2 6.2 5.9 5.8 7.2 4 .7 6.8 4.0 5.0 5.8 8.0 25 27 9.7 10 5.5 6.1 7.6 7.6 7.2 7.5 7.4 7.6 6.0 5.9 4.3 4.6 5.7 6.4 4.0 4.8 4.2 5.4 1.6 3.3 6.7 6.6 5.5 4.5 5.1 3.6 9.3 8.6 3.7 4.6 6.9 8.9 9.0 8.8 28 28 54 58 6.7 8.2
a Solutions of these samples contained a variety of foreign matter, such as fibers and large and fine particles. Probably this is the reason for the large differences between calculated and observed values. Equations 14 and 15 cannot be expected t o hold under such circumstances.
March 15, 1942
ANALYTICAL EDITION
217
Acknowledgment
hot water. Tests have shown that this causes a slight increase in color, but as it is roughly constant, it is ignored. There is no definite assurance that the exact relationships given in this paper will hold for coloring matter and turbidity present in beet sugars from other districts. If they do not, the correct relationships may readily be established b y the methods described. The problem is one of unusual complexity, and unfortunately no simple solution seems possible, barring the perfection of a method for rapid optical filtration of sugar solutions.
The advice of E. M. Hartmann is gratefully acknowledged.
Literature Cited Balch, R. T., ISD. ESG. CHEM.,ANAL.ED.,3, 124-7 (1931). (2) Keane, J. C., and Brice, B. A., Ibid., 9, 258-63 (1937). (1)
(3) Nees, A. R . , Ibzd., 11, 142-5 (1939). (4) Peters, H. H., and Phelps, F. P., Bur. Standards, Tech. Paper 338, 270-4 (1927). ( 5 ) Twyman, F., and Allsopp, C. B., "Practice of Spectrophotometry", 2nd ed., pp. 56-7, London, Adam Hilger, 1934. (6) Zerban, F. W., and Sattler, Louis. IR'D.ENG.CHEM..ANAL.ED., 8, 168-74 (1936).
Determination of K,O in Commercial Fertilizers Using 95 and 80 Per Cent Alcohol and Acid-Alcohol 0. W. FORD
AND
C. W. HUGHES, Purdue University Agricultural Experiment Station, Lafayette, Ind.
F
per cent alcohol. Since Hughes and Ford (4) reported increased solubility with rise of temperature, all work herein reported was done a t 18" C. for both 80 and 95 per cent acidalcohol and alcohol. Determinations were made on fertilizers of various analyses. A higher potash content was generally obtained when 95 per cent rather than 80 per cent acid-alcohol and alcohol were used.
OR several years many fertilizer chemists have believed
that potash determinations made by the official method have given low results due t o the use of 80 per cent alcohol and acid-alcohol in the determinations. The method to date has not been changed to correct this, even though the general referee on fertilizer of the A. 0. A. C. has often recommended the investigation of the solubility of potassium chloroplatinate in acid-alcohol and alcohol.
Procedure
Pierrat ( 5 ) gave the solubility of potassium chloroplatinate in various concentrations of alcohol at 14" C. but made no reference to the solubility at higher temperatures or under the conditions of the determination of the potash in fertilizers by the official method. Allen ( 1 ) reported a greater solubility of potassium chloroplatinate in 80 per cent than in 95 per cent alcohol but made no direct reference to the temperature, nor were the conditions identical with those involved in the determination of potash rein fertilizers by the official method. Hughes and Ford ported the solubilities of otassium chloroplatinate in 83 per cent alcohol and acid-alcoho!! at two different temperature levels, 18" and 38" C., but this work was done on potassium chloroplatinate precipitated from pure potassium chloride and was therefore not carried out under conditions exactly similar to those used in the determination of potash in fertilizers by the official method. Archibald, Wilcox, and Buckley ( 2 ) gave the solubilities of potassium chloroplatinate in alcohol-water mixtures at 20" C. but made no reference to acid-alcohol. Thus their results are not directly comparable to those obtained by the official method for potash in fertilizers. The above references, while important in themselves, are not general enough to include all the conditions to be met in the determination of potash in fertilizers by the official method.
The study is divided into three steps: 1. Comparison of the KzO values in mixed fertilizers by the official method (3, section 41, a), using aliquots of the same solution for both 80 and 95 per cent acid-alcohol and alcohol. 2. Comparison of the K20 values in potash salts by two procedures. Determination of the KzO in potash salts by the method for potash salts (3 section 41, b) using- both 80 and 95 per cent acidalcohol and alcohol. Determination of the KzO in Dotash salts. addine to the aliauot prepared for determination 1 gram of sodium &loride, by 'the method for potash salts (3,section 41, b) using both 80 and 95 per cent acid-alcohol and alcohol. 3. Comparison of the K20 values in a high-analysis complete fertilizer using a collaborative check sample (3,section 41, a) with 80 and 95 per cent acid-alcohol and alcohol. The same sintered-glass crucible (either Jena BG 3 or Pyrex M) was used in the filtration of the two aliquots of the same sample, using the concentrations of alcohol mentioned above. It was believed that this laboratory technique would avoid variations in filtration conditions that might occur had a padded Gooch crucible been used. All samples Tyere washed with approximately the same amount of alcohol (125 ml.). All KzO
(e)
'
The work reported in this study is a comparison of the potash contents of commercial fertilizers using 80 and 95
TABLE I.
cOMP.4RISOK O F AVER.4GES O F POT.4SH
DETERhlINBTIOSS O F
Low Complete Medium Complete Fertilizers, Fertilizers, 12-18 Unite= 16-24 Unitsb 95%
N o of analyses averaged Average result, yc L O Average difierence between alcohols, % I n d i r d u a l sample difference hetween alcohols, % '
80%
alcohol 10 3.80
alcohol
0.18
...,
10 3.67
95% alcohol 51
6.52 0.12
80%
alcohol 51 6.40
. .. . ... . .. . . .. ..
b1IXED
High Complete Fertilizers 25-40 Units0 95% alcohol 63 13.91 0 18
SO% alcohol 63
13.73
FERTILIZERS USING 80 AND 95 P E R CEST ALCOHOL
Medium Phosphate and Potash Fertilizers, 19-24 Unitsd 95% alcohol 37 11.40
.. .
0.19
.. . ...
0.03 -0.31
80% alcohol 37
High Phosphate and Potash Fertilizers, 25-40 Units' 95% alcohol 44
11.21
20.94
80% alcohol 44 20.78
... .. . . .. ...
0.16
...
Potash Salts 50 Unitsf 95% alcohol 16 50.96 0.23
80%
alcohol 16 50.78
...
0.li ... -0.31 , . -0.32 0.77 ... 0.45 . . .. . 1.70 1.88 Percentage L O increase Units distributed among the folluuing analyses: 03-64, 2-10-4, 2-12-2, 1-9-3, 2-8-6. 1-12-2, 1-14-2. b 2-12-6. 4-10-6, 4-12-4, 5-10-5, 6-8-6. 4-8-8.4-10-4. 0 312-12, 17-84, 2-12-12, 2-6-16, 3-6-16,3-8-16, 3-9-18, 4-24-12, 3-18-9, 2-16-8. d 0-14-6, 0-12-12, 0-10-10, 0 4 - 1 6 , e 0-21-9, 04-21, 0-20-20, 0-10-20, 0-16-24, 0-10-30. f 0-0-50. 0.02 -0.33 3.61
. .. .. . . , ..
,
.
0.00
0.02 -0.31 1.36
0.02 -0.34
. . ..,
