I N D UXTRIAL AND ENGINEERING CHEMISTRY
December, 1931
1479
NOTES AND CORRESPONDENCE Detergent Value of Sodium Metasilicate Editor of Industrial and Engineering Chemistry: There is probably no sales field in which there is keener competition, more misinformation, and pseudoscientific propaganda, than that of detergent alkalies. The article by Baker [IND. ENG. CHEM.,23, 1025 (1931)] contributes real information on metasilicate in this connection. There are, however, several discrepancies between the normality and weight per cent figures for sodium metasilicate in his Table IV, which need clearing up. For example, the 0.1 N solution has a weight per cent of 1.06, and the 0.01 N solution a weight per cent of 0.042, which are not consistent with each other. The failure of the article t o include results on the comparison with other alkalies in the last four kinds of tests, as was done in the first tests, detracts considerably from its value t o those interested in detergents in general. In view of the findings of Rhodes and Bascom [IND. ENG. CHEM.,23, 778 (1931)], the pH relations would indicate t h a t the silicate would fall between sodium hydroxide and trisodium phosphate in their Figure 3, thus making the order of increasing effectiveness when measured at equal pH as follows: borax, caustic soda, metasilicate, trisodium phosphate, and soda ash. Such a n assumption should be checked up experimentally, of course. The future paper promised by Rhodes and Bascom on silicates will be awaited with interest. GEORGELYNN THECOLUMBU ALKALI COMPANY BARBERTON, OHIO October 12, 1931
. . . . ....... * . . Editor of Industrial and Engineering Chemistry: The pointed Out George LYnn is obvious. The correct arrangement of the values is given in the following table: NORM A L I TY
PH
0.0002 0 0004 0.0010 0.0016 0.0020 0.0040 0.010 0.020 0.024 0.026 0.030 0.040 0.10 0.20 0.40
8.9 9.2 10.3 10.85 11.0 11.2 11.4 11.6 11.7 11.8 12.0 12.2 12.6 13 0 13.25
WEIGET
%
0.00212 0.00424 0.0106 0.017 0.0214 0.0420 0.106 0.212 0.252 0.262 0.318 0.424 1.06 2.07 4.07
VOyrfMO~
cc.
37 53 65 84 90 109 134 120 158 174 187 230 230 114 44
The practical laundry tests described in the latter part of the paper show definitely that a given soap solution has greater detergent power at a higher pH, thus correlating the scientific data given earlier in the paper with commercial practice. A comparison of the various alkalies under practical operating conditions would be interesting, and could form the basis of a complete paper on that subject. Rhodes and Bascom's [IND. ENG. CHEM., 23, 778 (1931)] point that the detergent action of a built soap solution cannot be entirely predicted from a knowledge of the alkalinity of the builder is well taken, as is also their point that the nature of the anion is an important consideration. For these reasons it is not safe t o make the kind of prediction indicated by Lynn as to the order of increased effectiveness of the alkalies considered. In comparing the work of Rhodes and Bascom with that of Baker, two points should be constantly borne in mind: (1) The former worked with a soap of much lower titer-i. e., 35" C. They did not describe the exact fatty acids contained in their soap, but generally speaking i t is safe to assume that their soap was more soluble and more easily hydrolyzed than the sodium stearate used by Baker. (2) Rhodes and Bascom worked at a lower temperature-i. e., 40' C., as compared with Baker's 60' C. These are factors which could easily produce extreme differences in the results obtained. In the commercial laundering of cottons, which form the greater bulk of the work, it is common practice to use a soap having a t least a 52" titer. The principal constituent of such a soap is sodium stearate. Such washing is usually carried out at approximately 60' C. In these respects, the later paper approaches more nearly t o commercial practice. In spite of different conditions used by the different authors, i t appears there is good agreement on several points in connection with the detergent assistance rendered a soap solution by an alkaline builder. (1) There is an optimum p H for each set of conditions. (2) A builder which does not increase the p H of the solution is of little or no value. (3) The detergent power of the solution is dependent upon both the p H and the anion present. (4) It is important that the builder used have a buffering action a t the desired pH. Certainly our knowledge of the detergency of built-up soap solutions is far from complete, and the future paper promised by Rhodes and Bascom will be received with much interest. C. L. BAKER PHILADELPHIA QUARTZC O . OF CALIFORNIA, BERKELEY, CALIF.
LTD.
October 22, 1931
New Bureau of Standards Standard Sample The U. S. Bureau of Standards has prepared a standard sample of high sulfur steel (0.60 per cent sulfur) containing 0.193 per cent carbon. This steel, though not of a commercial grade, was specially prepared t o provide a standard sample which would serve t o meet all conditions encountered in carbon determinations on commercial high sulfur steels. This standard, which is No. 105 in the series and certiiied for carbon only, costs $1.00 per sample of 150 grams. The sample may be paid for in advance with the order, or be sent parcel post C. 0. D. in the United
States and its possessions. All foreign shipments require prepayment, together with 20 cents additional postage. The Bureau of Stand:rds is also preparing a standard analyzed sample of Nitroalloy G" Steel (approximately 1.3 per cent chromium, 1.1 aluminum, and 0.20 molybdenum) which will be available for distribution about February 1, 1932. A list of standard samples, analyses, fees, etc., are given in Bureau of Standards Supplement to Circular 25, which can be obtained free of charge upon application to the Bureau of Standards, Washington, D. C.
