Fluorocolorimetric Determination of Blended and Oil in Oil-Water Emulsions
Oils
HENRY BENJAMIN 185 Blackthorn Ave., Toronto, Canada EXTRACTION METHOD T H E past few years the use of fluorescence in both qualiMany emulsions are subject t o contaminat,ionthat might intertative and quantitative analyses has advanced rapidly. fere with the visual colorimetric method and lead to eryoneous Many photoelectric and fluorescent instruments and techniques results. I n order to remove the interfering parts of the sample, have been developed and are now available t o the analyst. the following extraction method was developed: Thc application of this principle to analysis has speeded up and made more accurate the deTwo milliliters of the Samtermination of many elements ple were placed in a large and compounds. stop ered test tube and 10 ml. of etle, added. This was well The author of this article shaken, and 25 ml. of ti satuwaa called upon to determine rated solution of sodium chlothe concentration of sulfurized ride were added \o.break the cutting o i l s b l e n d e d w i t h emulsion. A small portion of the ether straight mineral oil used as a la er, now containing all the cutting coolant and also the oifin the samplr, was placed oil content of oil-wakr emulin stoppered glass tubes 0.47 sions. cm. (*/IC inrh) in diameter. It was not necessary to measure T h e o n l y m e t h o d availthe volume of this portion of able for c u t t i n g oils was the eample, as each tube was by means of viscosity, a slow of equd sire and all held the and messy procedura. It was same volume. Standards treated in exactly necessary to make up definite the same ninnner were preconcentrations of the blended pared and edorimetric comoils and determine viscosities parisons made. I t was neceson these standards, after which sar to prepare only one set anBseal them well in order to the viscosities of the samples prevent evaporation of the themselves were determined; ether, as these could be used such a procedure, while perindefinitely. haps accurate, was certainly Very close estimation of the time-consuming. total oil content in emulsions I n the case of the oil-water WATlO O r W M D I W C ACCNT :MlMLP*L OIL could be made by this method, emulsions, i t was found necesas any error caused by evaposary to break the emulsion by Figure 1. Viscosity of Cutting Oil ration of the ether was negligithe use of large quantities of ble and no measurable trace of sulfuric acid and then measure. by volume, the amount of oii in the samples. Both methods oil remained in the aqueous layer. Determination of oil in oil were very slow, and the latter was inaccurate. emulsions could be performed, by visual matching, to *O,l% (12.5 parts in 10,000). DETERMINATIONS BY FLUORESCENCE In the case of blended oils, all samples when checked colorimetrically with viscosity, showed a difference of only *2 SayI n order to improve the procedures and speed them up, use bolt seconds. Figure 1 shows the relationship of Sayboltseconds was made of the phenomenon of fluorescence excited by ultrato composition of blended oils in terms of ratios-Le., the proviolet rays. Determinations by this means could be made in as portions of blending agent t o mineral oil. This dserence many minutes as the older ones took in hours and were applicable brings a maximum error of only 3% a t t h loner end of the graph to all oils and waxes which exhibited any degree of fluorescence. and much less at the higher end. As the usual ratio of blending Oils and waxes which did not fluorasce could be estimated in the agent t o mineral oil lies about the center, the error is reduced same manncr by adding suitablc oil-soluble fluorescent dyes. proportionately. The blended oils referred t o do not contain water; they are not emulsions. Ultraviolet rays were supplied by a bank of four 2-watt argon bulbs, the vidible rays heing filtered out by a Wratten ultraviolet I n the estimation of emulsions by means of the ether-extracray filter. Strips of blotting aper, 0.6 X 3.75 cm. (0.25 X 1.5 tion method, smaller samples gave a much sharper color grada. inches), were impregnated wit{ standard samples of the oils made tion. u p to definite concentrat ions, and these, because of the fluorescent This principle was also applied to determine the efficiency of nature of the oil itself, produced a sharp gradation of colors. I t was then an casy matter to match the sampler to these standards. oil removal when metal parts were cleaned and washed by varioue As the concentra1.ions of the various blends ran be relnt,ed graphmethods. A trace of oil not visible to the naked eye became a p ically to the Viscosity, it is only necessary, when desired, to refer parent when excited by ultraviolet rays. t o an appropriate curve to express the fluorescentcolorimetric determination in terms of Baybolt seconds. ACKNOWLEDGMENT T o determine t,he concentrations of oil in the oil-water cmulsions, enmples of known oil eoncentrations were prepared and the The author must express his gratitude to Albert W. Bull, with. unknown sam le Mas colorimetrirally com Itred with them. The out whose assistance and criticism this method could not have standards eoupd he'used indefinitely, and i d not deteriorate over long periods of time. been developed.
IN
331
