October 15, 1931
INDUSTRIAL AND ENGINEERING CHEMISTRY
the absorption solution, after neutralization, to a beaker, adding bromine water, boiling, and precipitating with barium chloride. In the case of samples 11, 12, and 13 it was noted that the weights of barium sulfate obtained by this check corresponded to smaller quantities of sulfur than was indicated by the titrations. It was known that calcium and sodium hypochlorite have been used in refining crude sulfate wood turpentine ( 3 ) . This suggested that the difference between the total acidity obtained by the lamp combustion and the quantity of sulfur recovered as barium sulfate might be due to chlorine. The three samples on which the difference was found were retested with the lamp, and the absorption solutions were acidified with nitric acid and treated with silver nitrate solution. In each case silver chloride was precipitated, which on weighing indicated sufficient chlorine to account for the difference between total acidity by titration and sulfuric acid by precipitation of the barium sulfate. Chlorine was not found in the other samples tested. The results obtained with the various samples are listed in Table I.
SULFURADDED
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
%
%
None None None None None
None None None None None None None None None None
0.016 0.013 0.015 0.015 0.013 0.013 0.011 0,012 0 016 0.017
0.24 0.28 0 16
None None
Although the absorption method of determining sulfur in volatile fuels has been well tried out and has been in general use for some time, it was thought best to test the accuracy of this method for use with turpentine. A small quantity of ethyl mercaptan was added to gum spirits of turpentine previously found to contain no sulfur, and three 5-cc. portions of this solution were tested for sulfur, with the following average result:
%
0.054
0,052
FRACTION
of Tests of Various Samples for Sulfur with Kennedy L a m p KINDOF TURPENTINE SULFUR CHLORINE
Gum spirits Gum spirits Steam-distilled wood Steam-distilled wood Steam-distilled wood (s( Ida process) Sulfate wood (Sweden) Sulfate wood (Sweden) Sulfate wood (Sweden) Siilfate wood (U. S. A,) Sulfate wood (U. S. A,) Sulfate wood (U.S. A.) Sulfate wood (U. S.A.) Sulfate wood (U. S.A,) Sulfate'wood (U. S.A,) Sulfate wood (Canada)
SULFUR FOUHD
%
To test further the accuracy of this method for chlorine determination, solutions of purified pinene hydrochloride in both turpentine and ethyl alcohol were burned and the gases absorbed. Almost theoretical yields of chlorine were obtained. It was found that practically all the chlorine passed into the absorber in the form of hydrochloric acid. The results obtained when turpentine containing mono- and dichlorobenzene were burned in the Kennedy lamp indicated that the chlorine in these compounds is also converted guantitatively into hydrochloric acid on burning. On the other hand, bromine compounds of turpentine and benzene on burning in the Kennedy lamp, were found to yield bromine and bromic acid in about equal proportions, That the sulfur compounds in refined sulfate wood turpentine are concentrated in the lower boiling portions is indicated by the following results on fractions of sample 9:
Table I-Results
SAMPLE
355
SULFUR
% Distilling below 156' C. Distilling 156-158' C. Distilling 160-162° C.
0.030 0,008 0.004
The first 5 per cent of distillate of sample 15 obtained from distilling 200 cc. through an 8-inch (20.32-em.) Hempel column was found to contain 0.072 per cent sulfur. A similar concentration of chlorine compounds was found in the lower boiling fractions of certain of the samples of sulfate wood turpentine. This suggests that, where the presence of sulfur and/or chlorine in turpentine is in doubt, the results obtained by submitting 'the low boiling fraction obtained on distillation to the lamp combustion test can be relied on to determine definitely whether these two elements are present in the turpentine. Literature Cited (1) (2) (3) (4)
American Society for Testing Materials, "Tentative Standards," 1927 Bur. Mines, Tech. Paper S2SB (1927). Jobson, C. A,, U. S. Patent 1,493,454 (May 6, 1924). Kennedy, IND. E N G . CHEX.,20, 201 (1928)
Some Factors Influencing Soap Tests for Hardness' R. H. Kean and H. Gustafson INTERNATIONAL FILTER COMPANY, CHICAGO, ILL.
T
HE soap test method of determining hardness in water, while lacking the accuracy of an analytical procedure, is nevertheless capable of giving a very fair approximation of the true value in the hands of an experienced operator, and where it is used upon a single water for the purpose of measuring variations in hardness, the results have a considerably greater degree of reliability. There are certain factors, however, which may affect its accuracy even under these favorable conditions and, therefore, certain precautions must be observed to avoid the possibility of error. The necessity for these precautions arises from the fact that the test actually measures the soap-consuming power of the water rather than its hardness, and any condition of the water tending to promote or inhibit the formation of lather, or tending to decompose or precipitate the soap, may thus introduce errors into the determination. 1 Received April 8, 1931 Presented before the Division of Water, Sewage, and Sanitation Chemistry at the 81st Meeting of the American Chemical Society, Indianapolis, Ind March 30 to April 3, 1931.
This paper presents the results of an investigation of the errors introduced by certain conditions frequently encountered in zeolite water-softening practice-namely, by variation in the temperature of the water, by the presence of free carbon dioxide, and by the presence of certain salts of sodium. The experimental work was conducted with Boutron and Boudet soap solution, the standardization of which specifies that 40 cc. of water containing 225 p. p. m. of hardness as calcium carbonate shall require 2.4 cc. of soap to produce a lather. This is equivalent to 72 drops of soap, the droppers being calibrated to deliver 30 drops to the cubic centimeter. Thus 5 drops are equivalent to each 15 p. p. m. of hardness, or about 51/2 drops for each grain per gallon, making no allowance for the soap required to produce a lather with water containing no hardness. The temperature of the water has a very considerable influence on the soap test, there being an apparent increase in hardness with decreasing temperature. This is shown on Figure 1, which is a correction chart for this effect. The range
ANALYTICAL EDITION
356
0
/O
20
30
YO
- z&
&??pem?w@ BfHwi?L Figure 1-Correction Chart for Effect of Temperature on B. and B. Soap Test
below 10’ C. is the only part of the curve having significance for work in the field, but here the correction assumes real importance. For instance, in Chicago, where the winter temperature of the water is 1.5” to 2.0” C., the error amounts to 4 drops of soap. Since softener runs are often terminated when the effluent requires 5 drops, this test would indicate that the softener was incapable of delivering water softer than 1 grain per gallon, whereas in reality the water would be of “zero” hardness, requiring 1, or at most, 2 drops of soap. The effect of temperature is independent of the true hardness of the water up to 3 or 4 grains per gallon, the increase in soap requirement being identical for a “2-drop” water and a “15-drop” water. Like low temperature, free carbon dioxide is a very disturbing factor. I n the field its influence appears to be exceedingly erratic, owing in part to its fugacity, in part to the poor end point that it causes, and in part to the fact that its effect varies with the alkalinity of the water, the hardness, and other factors. Thus a simple correction chart for its influence cannot be constructed. However, its effect can be stated in more general terms, and a typical example is illustrated by Figure 2. For instance, the increase in soap required for a
Vol. 3, No. 4
carbon dioxide will cause a slightly greater increase in the soap requirement of a very soft water, say a “2-drop” water, than in the requirement of a harder water of 10 or 15 drops. Further, it may be seen from the chart that the influence of carbon dioxide decreases very markedly with increasing alkalinity of the water. This is owing to the repression of the hydrogen-ion concentration by the buffer action of the bicarbonate. The lower chart on Figure 2 illustrates the relationship between hydrogen-ion concentration, alkalinity, and carbon dioxide content. It shows how a given carbon dioxide concentration produces a greater depression of the pH in waters of low alkalinity. Furthermore, a comparison of the two charts demonstrates that the depression of the pH and increase in soap requirement go hand in hand-that is, the lower the pH, the greater the soap requirement. This is the significant point, for it indicates that the effect is a function of hydrogen-ion concentration rather than of the carbon dioxide itself. It is substantiated by the fact that a similar increase in soap requirement is obtained with distilled water, free of carbon dioxide, to which minute quantities of mineral acid have been added. In such waters the increase in soap requirement i%directly proportional to the quantity of acid added. The action is apparently a decomposition of the soap with liberation of fatty acid, The end point with mineral acid is very sharp, a copious lather being produced immediately when neutralization of the acid is complete. With carbon dioxide, however, as might be expected, the progressive shift of the equilibrium of the slightly ionized acids with successive additions of soap produces a poor lather and an uncertain end point. The difficulty caused by the presence of carbon dioxide and mineral acid may be completely removed by adding to the soap solution sufficient sodium hydroxide to neutralize the acidity of the water, which reestablishes very satisfactorily the proportionality between true hardness and drops of soap up to 3 or 4 grains per gallon. This expedient is very convenient for zeolite work where the waters tested lie within this hardness range, but the use of such alkaline soap for general field work is not recommended, because with larger amounts of soap solution the caustic concentration may become sufficient to effect some softening of magnesium waters and waters containing carbonate hardness. It has been indicated on Figure 2 that increased alkalinity of the water is without effect on the soap test. This was ascertained by adding different amounts of sodium bicarbonate to a water of known hardness. Sodium chloride and sodium sulfate likewise have no effect up to concentrations of 2500 p‘ p. m. (150 grains per gallon). The only action to be expected from these neutral salts would be a salting-out of the soap but, within the limits of concentration encountered in water treatment, this does not occur.
8.0
