ANALYTICAL EDITION
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held rigid by a clamp. The small pitman has a hardened steel button which engages in a groove cut in one link of the shackle, At mid-position the button does not touch the link, whereas the cam action at both ends of the stroke causes the link to weave as it would on the road, because of the up and down motion of the springs. Trays are set under the shackle to catch the grease which drips from each bearing point. The test is run for 12 hours and the amount of grease feeding out during the test noted. Some greases in a few hours will work out almost entirely, while others (like ordinary lime greases) will not feed at all. A Tryon shackle on a Chevrolet car was filled with a pressure grease and driven for 10,000 miles without attention. In several hundred miles the shackle started t o squeak and during the latter half of the test was very noisy. At the end of the test run, the shackle was completely worn out, yet three-fourths of the original charge of grease still remained, This apparatus has the advantage over a car, inasmuch as the severity of weaving is controlled and maintained constant for all tests, many miles of travel being represented by the overnight run of 12 hours. Furthermore the outfit, being portable, can be placed in a cabinet held a t any desired temperature, to furnish information on the feeding ability of various greases a t different temperatures. This outfit is not used as a control test but to demonstrate the superiority of one type of chassis lubricant over others. Chassis lubricant production is also occasionally checked for feeding ability with this machine.
CONCLUSIONS 1. As viscosity is the most important property of an oil, it is essential that accurate determinations be insured by the use of suitable instruments and proper methods. 2. Employment of the A. S. T. M. viscosity-temperature chart (D-341-32 T) and the Sinclair Viscosity index is invaluable as an aid to the proper understanding of oils and greases, 3. More use should be made of the Saybolt-Furol instrument and larger orifices for the determination of heavy lubricants, especially those containing small amounts of soap. The pressure viscometer is convenient and accurate for the determination of the apparent viscosity of fluid, semi-fluid, and soft plastic lubricants and even universal joint greases;
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however, consistency for plastic products seems to be more important. The higher the viscosity of the mineral oil and the greater the soap content, the greater will be the pressure viscosity. Insufficient pressure gives too high a value. Minimum values, obtained a t different temperatures, when plotted 3" high, fall on a straight viscosity line, representative of the lubricant. 4. I n classifying greases, the consistency is usually more important than the viscosity of the mineral oil in the grease. As consistency is the internal resistance of a grease to deformation, methods should be used which measure this property only. The following items should be observed: Deformation should be at a constant rate. The resistive force offered by the grease to its displacement should be a measure of the consistency. The cross-sectional area of the deforming tool (plunger) should be uniform, not conical or spherical. The adhesive property of the lubricant should be eliminated by avoiding contact of the shank with the lubricant at the time the resisting force is measured. The spike test and disk plunger (PD) test described above comdv with these reauirements. . Very careful attention should Le given to tem6erature. Control of 0.2' to 0.5" F. is possible,
5 . True viscosity a t low temperatures is very conveniently measured by means of the adherometer which gives data relative to the shifting ability of various gear lubricants. 6. Chassis lubricants should not drip, yet they should feed a t a proper rate in Tryon shackles. The drip and shackle test outfits are a great aid in the production of suitable chassis lubricants. The viscidometer has been in use for about 7 years and the pressure viscometer for 4 years a t several laboratories of the Sinclair Refining Company and have insured satisfactory control. The author is continually attempting to make improvements in test methods whenever an opportunity presents itself and hopes that others will be inspired by this paper to develop similar methods along the same lines. R E C ~ I V EOctober D 2, 1933. Presented before the Division of Petroleum Chemistry a t the 86th Meeting of the American Chemical Society, Chicago, Ill., September 10 to 15, 1933.
Determination of Fluorides in Natural Waters J. M. SANCHIS, Bureau of Water Works and Supply, City of Los Angeles, Calif.
T
HE wide publicity given to the findings of Kempf and
McKay (b), Churchill (2), and Smith, Lantz, and Smith (B), in regard to the relationship betweenmottled tooth enamel and the fluoride content of drinking water, has resulted in extraordinary interest in the presence of fluorides in potable waters. In April, 1933, the City of Los Angeles undertook, under the direction of H. A. Van Norman and R. F. Goudey, Bureau of Water Works and Supply, to determine the fluoride content of its sources of domestic water supply. This laboratory was then confronted with the necessity of adopting a suitable method for the quantitative determination of fluorine. After a thorough investigation of available procedures (2, 4, 7, 8), a modification of the method proposed by Thompson and Taylor was found to be most reliable, convenient, and specially suited to routine determinations when a large number of samples are to be analyzed a t any one time. The method, aa adapted to the determination of fluorides in natural waters, is as follows:
REAGENTS STANDARD SODIUMFLUORIDE SOLUTION. Prepare a stock solution containing 2.21 grams of c. P . dry sodium fluoride per liter. Dilute 10 ml. of stock solution to 1 liter (1 ml. equals 0.01 mg. of fluorine). INDICATOR. Prepare a stock solution as follows: (a) Dissolve 0.17 gram of alizarin sodium sulfonate in 100 ml. of distilled water. (6) Dissolve 0.87 gram of crystalline zirconium nitrate, c. P., in 100 ml. of distilled water. Add (a) to (b) slowly with constant stirring. Shake at intervals and allow to stand overnight. Dilute 20 ml. of stock sohtion to 100 ml. t o serve as indicator. When not in use, these solutions are best kept in a 0001 dark closet. Hydrochloric acid, 3 N . Sulfuric acid, 3 N .
PREPARATION OF STANDARDS To each of a series of nine 250-ml. Erlenmeyer flasks, add 0, 2.5, 5.0, 7.5, lo, 15, 20, 25, and 30 ml. of standard fluoride solution (1ml. equals 0.01 mg. of fluorine) made up to 100 CC. with distilled water. The suggested standards cover from 0 to 3 p. p. m. of
March 15, 1934
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
fluorine, which is a suitable range for potable water. The fluoride content of the unknowns can be estimated to the nearest 0.1 p. p. m. by interpolation. These standards are treated in a manner identical to that prescribed for the unknowns below.
PROCEDURE A 100-ml. aliquot of the sample to be anakzed, freed from
turbidity and suspended solids by filtration if nebessary, is placed in a 250-ml. Erlenmeyer flask. To each 100-ml. aliquot thus measured, and t o the prepared standards, add exactly 2.0 ml. of 3 N hydrochloric acid, 2.0 ml. of 3 N sulfuric acid, and 2.0 ml. of indicator solution.' Place flasks on a hot plate. Bring the contents rapidly t o the boiling point and remove soon after boiling begins. Do not allow to boil vigorously nor t o simmer for a long time. Four hours after cooling, or the following day, transfer the standards t o properly labeled 100-ml. matched Nessler tubes and make up to the mark with distilled water. Transfer each of the unknowns, in turn, to a 100-ml. Nessler tube and compare its color with that of the standards. If a reddish precipitate appears in any of the aliquots after cooling, disperse it by rapid whirling of the contents of the flask prior to their transfer to the Nessler tube and proceed with the determination as usual.
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manner. Duplicate determinations on a number of samples have given results which agree within 0.2 p. p. m. I n Table I, the fluoride recoveries obtained by the method here proposed from a series of natural waters are shown. The figures given are the average results of two sets of determinations made with the same waters on different days. TABLEI. FLUORIDE RECOVERY FROM NATURAL WATERSBY MODIFIED ZIRCONIUMNITRATE-ALIZARIN SODIUM SULFONATE METHOD LABORATORY NO.
DESCRIPTION
FLUORIDE FLUORID. IN FLUORIDIO RacovSAMPLE ADDED ERRD P.p.m. P.p.m. P.p.m.
287 Headworks line (infiltration gallery water) 0.4 297 Barnes City well 0.3 326 Marston's well 0.5 327 Owens River a t Thompson's Ranch 0.4 328 Mammoth Creek (above lava) 0.2 329 Hot Creek a t Co. Bridge 2.1 331 Owens River a t Crooked Creek 1.2 333 Fish Slough 0.9 354 Lomita Well No. 5a 0.6 355 Wilmington Well No. 13a 0.6 403 Shaft No.2 near Silver Lakeb 0.3 a Slightly colored waters. b Sample contained 1.5 p. p. m. hydrogen sulfide.
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.4 1.3 1.4 1.3 1.1 2.8 2.2 1.8 1.5 1.4 1.2
DISCUSSION OF METHOD Organic matter and phosphates, if present in the samples Thompson and Taylor, in their method for determining in appreciable amounts, tend to throw some of the indicator fluorides in sea water (E), recommend the preparation of out of solution. If the reddish precipitate formed is slight, fluorine standards with a solution of salts having a sulfate-to- it is possible to disperse it by rapid whirling of the contents chloride ratio analogous to that of sea water. The direct of the flask and to compare the color as usual without diffiapplication of this procedure to fresh waters did not seem culty or material sacrifice of accuracy. I n extreme cases practical because the wide fluctuation of their chloride to when the amount of precipitate is such that the matching sulfate ratio, as well as of the actual amounts of these radicals of color cannot be made satisfactorily, the method proposed present, almost necessitates the preparation of a set of stand- by Willard and Winter (9) or its modification as suggested ards for each sample to be analyzed. This procedure, how- by Boruff and Abbott (1) may be used to advantage. ever, has been recently suggested, with some modifications, SUMMARY by Elvove ( 3 ) . The substitution of standards made up with distilled water The zirconium-alizarin method for the colorimetric deterfor those prepared with a solution of the salts present in mination of fluoride has been modified for the quantitative the unknowns did not prove successful when hydrochloric estimation of the ion in potable waters. The suggested proacid only was used for the acidification of samples and stand- cedure makes possible the use of distilled water in the preparaards. Tests, made on a series of synthetic waters, indicated tion of the standards instead of synthetic water of similar that the presence of sulfates interfered seriously with the mineral content as that of the water being analyzed. This quantitative determination of fluorides. permits the use of one set of standards for the determination Attempts to remove the sulfates by precipitation with of fluorides in any number of fresh water samples regardless barium chloride, followed by filtration through asbestos, of the composition of their mineral content. The method were not altogether satisfactory. However, the substitution has been found to be reliable, convenient, and specially suited of half the amount of hydrochloric acid, to be added to both to routine determinations when a large number of samples the unknowns and standards, by an equivalent amount of is to be analyzed a t any one time. sulfuric acid, effectively eliminated the interference of sulfates in the amounts normally found in fresh waters. Under LITERATURE CITED these conditiojs it was necessary to increase the concentraBoruff, C. S., and Abbott, G. B., IND.ENG.CHEM.,Anal. Ed., tion of the indicator in order to obtain a color range, varying 5 , 236-8 (1933). from pink to yellow-green, which would permit an easy Churchill, H. V., IND.ENG.CHEY.,23, 996-8 (1931). matching of the standards with the unknowns. Elvove, E., Pub. Health Rpts., 48, 1219-22 (1933). Foster, M. D., J. Am. Chem. Soc., 54, 4464-5 (1932). The results of several hundred determinations, made with Kempf, G. A., and MoKay, F. S., Pub. Health Rpts., 45, 2923 synthetic waters by the method here proposed, indicate that (1930). chlorides, sulfates, bicarbonates, sodium, calcium, and magSmith, M. C., Lantz, E. M., and Smith, H. V., Univ. Ariz. Coll. nesium up to 500 p. p. m.; manganese up to 200 p. p. m.; Agr., Tech. Bull. 32 (1931). Smith, M. C., and Smith, H. V.. Ibid., 43, 217-18 (1932). silicates up to 50 p. p. m.; phosphates, boron, copper, and Thompson, T. G., and Taylor, H. J., IND.ENO.CHEM.,Anal. iron up to 5 p. p. m.; and sulfides up to 2 p. p. m. do not Ed., 5 , 87-9 (1933). interfere with the quantitative determination of fluorine. Willard, H. H., and Winter, 0. B., Ibid., 5 , 7-10 (1933)+ The permanency of the color allows the estimation to be made whenever convenient, within a day or so, after 4 hours RJWEIVEDNovember 3, 1933. following the heat treatment, provided that the samples and standards are treated a t the same time and in an identical U. S. EXPORTS OF SCIENTIFIC INSTRUMENTS DECLINE. The 1 The intensity and shade of the color produced depend on the concenvalue of scientific and rofessional instruments exported from the tration of indicator and of each of the acids in the aliquots. I t is therefore United States declinefl5 per cent in 1933 compared with 1932, necessary t o add identical amounts of these reagents t o both standards and according to figures compiled in the Commerce Department. unknowns in order t o obtain the maximum possible accuracy in the deterThe totals for the two years were $3,710,662 and $4,406,527, mination. The use of narrow-bore 2-ml. pipete has been found satisfactory respectively. Only two divisions of the professional instruments for the addition of acids and indicator group recorded increases.
