DECEMBER, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
are able t o control the yield of our blends. By that we mean we turn out a strong batch and then a weak batch, thus giving us leeway so as to be able to standardize to strength by mixing the two blends. In the few cases where we have had to add a standardizing material we have used Glauber salt. The soluble forms of iron blue are generally made by treating the water-insoluble form with sodium ferrocyanide or oxalic acid. Such products are not truly soluble but they are colloidal when added to water and can be used like sQllilMedyestuffs, Soluble iron blue is precipitated from its colloidal solutions by small amounts of certain metallic salts such as those of calcium, aluminum, and an excess of iron salts such as iron sulfate or iron chloride. Most permanent blue-black inks will contain sulfate or chloride, or both, from the use of ferrous sulfate (which, with the tannic and gallic acids present, forms the insoluble deposit on the paper which makes the writing "permanent") and from hydrochloric or sulfuric acids, and from any standardizing salts which may be present in the dyes used. However, there are writing fluids to which have been added no acid or salt, and which use a d y dyes for the color. I n such inks the only source of chloride and sulfate is material that the dye manufacturer may have used for standardizing the dye or small amounts from the water supply. Thus, it is conceivable that certain kinds of inks may contain no chloride or sulhte and a h that the same brand
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and formula may contain different amounts with different batches of dye.
Acknowledgment We wish to express our thanks to the W. A. Sheaffer Pen Company for permission to publish these results, to the dye manufacturers ( I ) for the information they furnished, to John E. Hauck for the photography and assistance in the experimental work, and to Roger Macdonald for helpful suggestions.
Literature Cited (1) American Aniline Products Co., private
communication, April
Calco Chemical Div., American Cyanamid Co., Ibid., March 21; Eimer & Amend, Ibid., March 2 5 ; Fezandie & Sperrle, Inc., March 21; Geigy Co., Inc., April 4; General Dyestuff Corp., March 19;Harmon Color Works, Inc., April 8; Imperial Paper & Color Corp., April 5; Paul Uhlich & Co., Inc., April 3; Standard Ultramarine Co., March 22, 1940. (2) Federal Standard Stock Catalog (Section IV, Part 5), Fed. Spec. for Ink, Writing. TT-1-563 (Par. F-4b), Washington, D. C., U. S. Government Printing Office, 1931. (3) Finn, John, Jr., and Cornish, R. E., News Ed. (Am. Chew. SOC.), 18, 174 (1940). (4) Olsen, J. C.,Van Nostrand's Chemical Annual, 7th ed. p. 93, New York, D.Van Nostrand Co., 1934. (5) Rowe, F. M., Colour Index, 1st ed., p. 309,Bradford, Yorkshire, SOC.Dyers and Colourists, 1924. (6) Vail, J. G., Philadelphia Quartz Co.. Bull. 179,5 (1934). 5;
Nomograph for Surface Tension of Ethyl Alcohol-Water Mixtures D. S. DAVIS, Wayne University, Detroit, Mich.
B
ONNELL, Byman, and Keyes ( I ) presented excellent data covering the surface tension of ethyl alcoholwater mixtures. The solutions studied had concentrations sf 2.33, 5.94, 15.9%29.67, 43,64,61.10, 75.68, and 92-12 per cent ethyl alcohol by weigh&while the temperatures wcae at uneven intervals between 20" C. and the atmospheric boding points. In view of the i m p o r b e e of the data it seems worth while to provide a convenient and accurate means of interpolation. Surface tension, y, can be plotted linearly with temperature, t, according to the expresskn, r=a+bt
where a and b aire specific for each concentration. A close study of the variation af a and 6 with conceatratiom, using the La Grange intmpolation Eormuh (2) whem necessary, enables construction of the acwmpanying h e coordinate chart. The chart permits ready percentage and temperature interpolation, a straight line cutting the three axes in value&consistent with the original data. As an illustration, a solution conbinkg 10 pen eent ethyl alcohol by weight has a surface tension of 44.0 dynes per cm. a t 54" C, Surface tension data for puxe water are from the International Critical Tables (3).
Literature Cited (1) Bonnell, W. S., Byman, L., and Keyes, D. B., IND. ENQ.CHBIM.. 32,532 (1940). (2) Davis, D.S.,Chem. & Met. Eng., 45, 383 (1938). (3) International Critical Tables, Vol. IV, D. 447, New York. MoGraw-Hill Book Co., 1928.
