August 15, 1943
ANALYTICAL EDITION
overcome by the formation of a complex of molybdenum with citric or tartaric acid.
Literature Cited (1) Abegg, R., and Auerbach. F., “Handbuch der anorganischen Chemie”, Vol. IV, Part 1, 11, p. 1018, Leipaig, S. Hirzel. 1921 (2) Barber, H. H., and Kolthoff,I. M., J. Am. Chem. Soc., 50, 1625 (1928).
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Ibid., 51, 3233 (1929). Feigl, F., Z . anal. Chem., 74, 389 (1928). Kolthoff, I. M..Ibid., 70, 397 (1927). Lancien, A., Compt. rend., 144, 1434 (1907). (7) Petukhovrt, E. V., Zavodskaya Lab., 9, No. 1, 108 (1940). ( 8 ) Yagoda, H., and Fales, H. A., J . Am. Chem. SOC.,58, 1494 (1936).
(3) (4) (5) (6)
P R E ~ E N T Bbefore D the Division of Analytical and Micro Chemistry a t the CHEMICAL SOCIETY, Detroit, Mich. 105th Meeting of the AMERICAN
Analvsis of Commercial Oil Emulsions and Wax Dispersions FRANK M. BIFFEN AND FOSTER DEE SNELL Foster D. Snell, Inc., 305 Washington St., Brooklyn, N. Y.
Oil emulsions, which may or may not contain suspended solids, are analyzed by first distilling off any water-immiscible solvent. Benzene is then added and distilled with continuous return, carrying with i t the water which does not return to the sample. This avoids formation of troublesome emulsions during the conventional extractions of the oil phase. This procedure is sufficiently longer than the conventional extraction to be inadvisable for simple oil emulsions if they are readily extractable with ether. The aqueous distillate contains any alcohol. By centrifuging if necessary and evapora-
ETHODS of analysis of emulsions and suspensions as previously published (2) have been revised with further experience to simplify the procedures and provide greater accuracy. One major change has been in methods applied to oil emulsions, which may or may not contain suspended solids, to give more complete separation, avoid troublesome extractions in a separatory funnel, and prevent oxidation of the oils present. The importance of water-base wax suspensions has increased steadily and the types of soap stabilizers used have been complicated by commercial introduction of numerous amines. For brevity many conventional methods of analysis are referred t o only briefly without details.
Oil Emulsions The products in this class may vary from a medicinal oil emulsion to automobile cleaner-polishes. Many of the products contain fractions, such as petroleum naphtha, \+hich are volatile mith steam. Glycerol is often present, alcohol occasionally. Some products contain from a trace to 2 per cent of waxes. The emulsifying agents encountered individually or as mixtures include 1 to 5 per cent of bentonite, varying with consistency and type of clay, usually less than 1 per cent of various gums, and surface-active agents, usually sulfated oils or soaps. The latter are apt to be amine salts of fatty acids, but occasionally the other members of the class are present. Persistence of soap and gum emulsions is a problem in conventional extractions which to a greater or lesser degree extends to other surface-active agents. Of all the emulsifying agents mentioned, bentonite is the worst offender. Ethern-ater emulsions stabilized with it will often not break even
tion of benzene, the oil is recovered without undue oxidation. The solid residue is then separated by conventional methods into alcohol-soluble, chlorohydrocarbon-soluble, w-ater-soluble, and mineral fractions for separate analysis. Amine emulsifiers are determined on another portion of the original sample but all other determinations are carried out on the single sample. Improved methods for analysis of water-base wax dispersions provide for precipitation by acid, followed by separation and approximate identification of resins, wax, amines, etc.
on prolonged centrifuging or on addition of minor amounts of alcohol ( I ) . The method provides for first distilling any solvent volatile with steam, then adding benzene and distilling water with it. The oil, emulsifying agent, and abrasive, if any, remain in the flask in excess benzene and receive more conventional treatment. Only a single sample is required unless a nitrogen determination is required for estimation of amines.
Outline of Separation of Commercial Oil Emulsions Original sample SteLrn distillation - Immiscible solvent, water, alcohol I Reflux nith henzene - Water, sometimes alcohol I
Centrifuge cold
- Oils
and bulfated oils in benzene solution
i
Extract with hot alcohol - Glycerol. soap, fatty acid in alcohol I
Extkact nith hot,C?H,Cl, - Waxes in C2H3C11 Exiract with hot water - TI-ater-soluble gums RIikeral matter Generally speaking, it is not necessary to use this method if the emulsion is of oil in water without added mineral mat-
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 15, No. 8
ter and t h e emulsion will break down readily with ether or petroleum ether.
SEYARATION OF O m AND BENZENE-INSOLUBLE SOLIDS.The oils are now in hensene solution. Thoroughly agitate the contents of the flask to suspend the sediment and transfer to % 250ml. centrifuge bottle. Rinse out the flask into the bottle with a few milliliters of benzene, and centrifuge the mixture. No water being present, a sharp separation occurs. Decant off the henBene solution and add more warm heneene. Thoroughly break up the solids caked in the bottom of the bottle, shake vigorously to wash this with the benzene, and centrifuge. Repeat the process until the benzene extraot is colorless. Usually a total of three or four extractions is sufficient. OILS. Combine the benzene extracts and evaporate carefully, 8. convenient technique being to collect the hensene in an empty Soxhlet tube. Evaporate the final residues of benzene on a water bath and dry the oils far a few minutes in an o v a , avoiding overheating with consequent oxidation or loss by evaporation. Cool and weigh the oils. Allow the oil fraction to stand overnight in a desiccator. If saponifiable oils, castor or sulfated castor, for example, are present they will set,tle out as a viscous layer below the mineral oil. Chill the flask and contents, add chilled petroleum ether an the
petrolekm ether. Evaporate off th; petroleum ether from these flasks to obtain the mineral and saponifiahle oils separately. Analyze these in the usual manner. ALCOHOL-SOLUBLE MATTEU. Break up the residue in the centrifuge bottle and shake well with 75 ml. of warm 95 per cent alcohol is. I). 3A will do). Cool to room temperature and cen-
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In case an alkali-metal soav was originally Dresent, which is
nresent ohecks hv ealcklation with the entire amount of alcohoi-
of this fraction. Evaporate the alcohol and proceed
