January 15, 1935
ANALYTICAL EDITION
Assoc. Official Agr. Chem., Report of Subcommittee C, J.Assoc. Ofichl Agr. Chem., 14, 63 (1931). Biazzo, R., Ann. chim. applicata, 16, 96 (1926). Bishop, E. R., Otto, I. G., and Baisden, L., J. Am. Chem. Soc., 56, 408 (1934). Blumberg, H., and Rask, 0. S., J. Nutrition, 6, 285 (1933). Callan, T., and Henderson, J. A. R., Analyst, 54, 650 (1929). Clarke, S. G., and Jones, B., Ibid., 54, 333 (1929). Currie, A. N., Biochem. J.,18, 1224 (1924). Davies, W. L., J . Dairy Research, 3, 86 (1931). Drabkin, D. L., and Waggoner, C. S., J . Biol. Chern., 89, 51 (1930). Elvehjem, C. A., and Hart, E. B., Ibid., 91, 37 (1931). Elvehjem, C. A., Hart, E. B., and Steenbock, H., Ibid., 83, 27 (1929). Elvehjem, C. A,, and Lindow, C. W., Ibid., 81, 435 (1928). Fischer, H., and Leopoldi, G., 2. angew Chem., 47, 90 (1934). Flemine. R.. Anukist. 49. 275 (1924). Gebhar& T. H., and Somm&, H.’H., IND.ENQ.CHIN., Anal. Ed., 3, 24 (1931). Grendel, F., Pharm. Weekblad,67, 913 (1930). Guthrie. E. S., Roadhouse. C. L., and Richardaon. G. A,, Hilourdh. 5.426 (1931). Haddock, L. A,, i n d Evers, N., Analyst, 57, 495 (1932). Harry, R. G., Ibid., 56, 736 (1931). Inouye, J. M., and Flinn, F. B., J.Lab. Clin. Med., 16,49 (1930). Keil. H. L.. and Nelson, V. E., J. Biol. Chem., 93, 49 (1931). King, C. A,, and Etzel, G., IND.ENO.CHEM.,19, 1004 (1927). Lampitt, L. H., Hughes, E. B., Bilham, P., and Fuller, C. H. F., Analyst, 51, 327 (1926). McFarlane, W. D., Biochem. J.,26, 1022 (1932). Mehurin, R. M., J. Assoc. Oficial Agr. Chem., 15, 541 (1932). Ibid., 16, 330 (1933). Pope, T. H., Analyst, 57, 709 (1932).
23
(31) Popoff, S., Jones, M., Tucker, C., and Becker, W. W., J . Am, Chem. Soc., 51, 1299 (1929). (32) Pregl, F., “Quantitative Organic Microanalysis,” tr. by Fyleman, 2nd English ed., pp. 167,175, Philadelphia, P. Blakiston’s Son & Co., 1930. (33) Quam, G. N., and Hellwig, A,, J . Bid. Chem., 78, 681 (1928). (34) Quartaroli, A,, Ann. chim. applicata, 17, 361 (1927). (35) Redfield, A. C., Coolidge, T., and Shotts, M. A., J. Bid. Chem., 76, 185 (1928). (36) Rems, E., 2. Untersuch.Lebensm., 64, 545 (1932). (37) Sarata, U., Japan. J . Med. Sei., 11, Biochem., 2, 247 (1933). (38) Ibid., 2, 261 (1933). (39) Scott, W. W., “Standard Methods of Chemical Analysis,” 4th ed., revised, Vol. 1, pp. 197-9, New York, D. Van Nostrand Co., 1925. (40) Sisley, M. P., and David, M., Bull. soc. chim., (IV) 47, 1188 (1930). (41) Supplee, G. C., and Bellis, B., J. Dairy Sci., 5, 455 (1922). (42) Thatcher, R. W., J. Am. Chem. SOC.,55, 4524 (1933). (43) Thomas, P., and Carpentier, G., Compt. rend., 173, 1082 (1921). (44) Walker, R., J. Assoc. Oficial Agr. Chem., 13, 426 (1930). (45) Ibid., 14, 450 (1931). (46) Warburg, O . , Biochem. Z . , 187, 255 (1927). (47) Williams, W., J. Dairy Research, 3, 93 (1931). (48) Wright, N. C., and Papish, J., Science, 69, 78 (1929). (49) Yoe, J. H., “Photometric Chemical Analysis, Part I. Colorimetrv.” New York. John Wilev & Sons. 1928. (50) Zbindei,’C., Lait, 11, i 1 3 (1931).(51) Ibid., 12, 481 (1932). (521 Zondek, S. G., and Bondmann, M., Klin. Wochschr., 10, 1528 (1931). RECBXYED August 21, 1934.
Determination of Fluorine in Drinking Water Comparison of Several Methods and Establishment of Toxic Concentration by These Methods H. V. SMITH,University of Arizona, Tucson, Ariz.
S
INCE the discovery that fluorine in drinking water (8) is the cause of mottled enamel of teeth, much interest has been manifested in the analysis of water for this element. When the first studies of the cause of mottled enamel were made a t the University of Arizona in 1930, the volatilization method of Jacob, Ross, and Reynolds (6) for the determination of fluorine in rock phosphate was adapted to water analysis, and used in determination of the fluorine present in waters known to cause mottled enamel. This method consisted essentially of the distillation of fluodne as silicon tetrafluoride from the dry water residue into water, and titration of the hydrofluosilicic acid thus formed with a standard base. From the use of this method, it appeared that the minimum concentration of fluorine in water which would produce mottled enamel lay between 0.72 and 2.0 parts per million. This preliminary work was followed by a more intensive study of the occurrence of mottled enamel and its correlation with the concentration of fluorine in water supplies (9). In 1931 practically all parts of Arizona were visited, the teeth of the native inhabitants examined, and the water supply was sampled for analysis. Subsequently the fluorine analyses were made by the Fairchild method (3) as modified and used by Churchill (1). In this method the fluorine combines with ferric iron which is added in excess as ferric chlo-
ride. The uncombined iron is determined iodometrically and the amount of fluorine is calculated. The analysis of about 160 samples of water by this method showed a fluorine content ranging from 0.2 to 12.6 parts per million. Endemic areas in which mottled enamel was of the rather severe type were found to be using water with a fluoride content in excess of 5.0 parts per million. The minimum concentration of fluorine in water which was observed to produce mottled enamel appeared to lie between 2.0 and 2.7 parts per million. With this information a t hand it was possible to predict with considerable accuracy the probable effect of any water on the teeth. As a result of the great interest in the problem of fluorosis, other methods of fluorine determination have since been developed and the limitations of the Fairchild method, when applied to water, brought out. Foster (5) has pointed out that the Fairchild method of analysis gives high results when no correction is made for sulfates, for they have an effect similar to fluorides. The writer has also noted that organic matter in waters renders the Fairchild method unreliable because it has an iodine-consuming power which leads to a high fluorine result. It is the purpose of this paper therefore to compare the results obtained by some of the more recently developed methods of fluorine analysis, and to establish the toxic
INDUSTRIAL AND ENGINEERING CHEMISTRY
24
Vol. 7, No. 1
CONTENT OF POTABLE WATBRS CORRELATED WITH THEIREFFECT UPON TEETH^ TABLEI. FLUORINE LOCATION
r
Fairchild
METHOD OF ANALYBIB Foster Willard Sanchis A.
Aj o Aztec Buckeye Cochise Concha Douglas Eager Florence Gila Bend Gila River JoseDh City Hayden Laveen Mammoth Mesa (rural) Menlo Park
5.8 12.0 2.4 2.0 7.5 5.2 1.8 2.8 10.6 3.0 2.8 3.0 2.5 6.0 3.1 2.7
2.4 6.8 1.2 0.9 4.7 2.4 0.9 0.9 6.7 1.0 1.0
2.2 7.2 1.5 0.9 3.9 2.4 0.9 0.9 6.8 0.9 1.0 1.3 1.6 3.7 1.0 1.0
... 1.3
3.9 1.1 1.1 8.
LOCATION
c
Fairchild
METHOD OF ANALYBI~ Foster Willard Sanohis
WATERB WHICH CAD'BE MOTTLED ENAMEL
2.8 8.0 1.3
... ...
2.5
...
1.1 6.8
...
0.9 1.4 1.5 4.0 1.0 1.0
N. Gila School Oracle Ha den (rural) SaJord (rural) Roll Roll School Roosevelt School Dist. San Xavier Sentinel St. David St. David To ock Wifson, Ida. Winkleman Sentinel
9.1 3.0 7.5 3.0 8.7 3.3 3.5 3.0 9.3 4.6 6.0 4.7 16.8 2.8 7.7
1.9 1.1 3.0
1.1
2.4 1.6 3.2
2.4 1.3
... ...
...
4.7 1.3 1.5 0.9 6.0 1.1 3.6 1.0 13.2 1.1 5.9
1.3 1.9 1.0 5.5 1.8 3.4
1.3 5.0 1.5 1.7 0.9 5.8 1.6 3.4 2.8
11.1 1.1 4.6
1.0 4.8
0.5 0.5 0.2 0.6 0.4
0.3 0.6 0.6 0.6 0.2
0.3 0.1 0.1 0.3 0.2 0.4
0.4 0.3 0.4 0.4 0.2 0.4
...
...
WATERS WHICH DO NOT CAUBE MOTTLED ENAMEL
...
0.4 1.8 ... Avondale 0.3 0.4 0.3 0.9 Benson 2.1 0.8 0.8 0.7 Chandler 1.2 0.2 0.6 0.3 Clarkdale 0.9 0.4 0.3 0.3 Concha (SJiring) 0.1 0.3 0.4 0.3 Fairbanks 0.5 0.2 0.3 1.1 Flagstaff 0.4 0.3 0.5 2.5 Holbrook 0.2 0.1 0.3 1.1 Jerome 0.1 0.3 1.0 ... Miami 0.4 0.4 1.7 0.6 Morenoi ... 0.6 0.7 1.9 Nogales 0.5 0.5 0.2 0.8 Pima a All fluorine solutions used as standards were made from sodium fluorite obtained from the U. S. Bureau of Standards.
concentration of fluorine in water when the analysis is made by any of these methods.
EXPERIMENTAL The methods investigated include those of Willard and Winter (II), Foster (5), and Sanchis (7), and the results of analysis by these methods are compared with each other and with the Fairchild method. In the method of Willard and Winter (11) the fluorine is distilled off as hydrofluosilicic acid in the presence of glass beads and perchloric acid and the distillate is titrated with thorium nitrate, using zirconium nitrate and alizarin red or alizarin red alone as an indicator. The Foster method (4) assumes that iron combines with fluorine to form the complex NasFeFB,which does not react perceptibly with ammonium thiocyanate t o give the characteristic red color of ferric thiocyanate. Ferric chloride is therefore added to the sample and the excess determined colorimetrically. In this method, ion9 such as sulfates and chlorides which have the ability t o remove iron from reaction are compensated for by adding additional iron to the solution. Sanchis (7) also used alizarin red and zirconium nitrate as an indicator in his method of fluorine analysis. The method is a modification of the Thompson and Taylor (IO) method for the determination of fluorine in sea water. In the adaptation for the analysis of fresh water, chloride and sulfate effects up to 500 parts per million are nullified by the addition of hydrochloric and sulfuric acids. I n order to determine the minimum concentration of fluorine in water which would definitely mottle the teeth of those who drink the water during.the period of formation of their permanent teeth, the fluorine content of waters of known association with this dental defect were tested by the methods described above. The results of these analyses correlated with their effect upon teeth are presented in Table I. Further evidence is given that the results of fluorine analyses of water by the Fairchild method are abnormally high. However, the fluorine content of a given water as analyzed by the methods of Willard, Foster, or Sanchis is essentially of the same order. For example, the fluorine content of water from the rural Mesa district was found to be 1.1 parts per million by the method of Sanchis, 1.0 by the Foster method, and 1.1 by the method of Willard. The analysis of this same water by the Fairchild method gave a result about three times higher (3.1 p. p. m.) The results of the analysis of 55 waters by these four methods are grouped into two classes: waters which are known t o be associated with mottled enamel, ]and those which
Pomerene Pomerene School Presoott Red Rock Saff ord Sonoita Superior Tombstone Wickenberg Willcox Winslow Yuma
1.4 0.9 1.1 1.0 0.5 0.6 1.1 0.2 1.5 1.2 0.7 2.0
...
...
0.5 0.8 0.1 0.7 0.4 0.3 0.3 0.0 0.2 0.2
... ...
have been found not to cause mottled enamel. This division is based on tooth examinations made by Smith (9). The 29 waters associated with mottled enamel, as analyzed by the Foster, Willard, and Sanchis methods, have a fluorine content varying from 0.9 to 13.2 parts per million. Twentyfive waters which did not cause mottled enamel had fluorine contents ranging from 0.1 to 0.8 part per million. Severe mottled enamel of the deeply stained and pitted type appears to be associated with waters containing well over 2.0 parts per million of fluorine. Waters containing from 1 to 2 parts per million were always associated with a mild to moderate type of this dental defect. The lower limit of toxic fluorine concentration-i, e., concentration in water which will produce a very mild type of mottled enamel -appears to be from 0.9 to 1 part per million. It was noted also that other waters with a fluorine content of 0.7 to 0.8 part per million did not have a toxic effect upon the teethfor example, the water supply of the city of Chandler. This community, however, is surrounded by areas in which mottled enamel does occur and in all probability has a fluorine content which is just below the toxic concentration. It is difficult to establish the exact fluorine concentration in a water supply which will damage the teeth of its users, for other factors such as quantity of water consumed, length of time the water was used, and perhaps nutritional conditions of the subjects are variable. However, the evidence at hand indicates strongly that any water with a fluorine content of 0.9 part per million or over (when analyzed by the Foster, Willard, or Sanchis methods) is dangerous from the standpoint of probable damage to the teeth. No Arizona water has yet been found containing as much as 1.0 part per million of fluorine which has not been demonstrated to cause mottled enamel, and no water with a fluorine content less than 0.8 part per million has been found to be associated with mottled enamel. As Dahle (2), associate referee for the Association of Official Agricultural Chemists, found little difference in results obtained between the Steiger and Foster methods, it is perhaps safe to conclude that the toxic concentration of fluorine is similar when determined by the Foster, Willard, Sanchis, or Steiger methods, and has as its lower limit 1.0 part per million or slightly less.
SUMMARY AND CONCLUSIONS A comparison of the fluoride content of 44 waters has been made, using the Fairchild, Foster, Willard, and Sanchis methods.
A N A L Y T I CA L E D I T I O N
January 15, 1935
Results obtained by the Foster, Willard, and Sanchis methods are in close agreement. The Fairchild method gives results which average two to three times higher than results by other methods. Concentrations of fluorine of 0.9 to 1.0 part per million and greater (Foster, Willard, or Sanchis methods) have been found associated with mottled enamel. Concentrations of fluorine as high as 0.7 to 0.8 part per million (Foster, Willard, or Sanchis methods) have been found in waters not associated with mottled enamel. No water has been found containing more than 1.0 part per million (Foster, Sanchis, or Willard methods) which is not definitely associated with mottled enamel. No water has been found containing less than 0.8 part per million which is known to cause mottled enamel.
RCF
c
2,000,000
700 :500 7400
F
00.00 0
'
QOOO
2000
:7 5
25
LITERATURE CITED (1) Churchill, H. V., IND. ENQ.CHEM.,23, 996-8 (1931). (2) Dahle, Dan, private correspondence. (3) Fairchild, J. G., J. Wash. Acad. Sci., 20, 141-6 (1930). (4) Foster, M. D., IND.ENG.CHEM.,Anal. Ed., 5, 234 (1933). (5) Ibid., 5 , 238 (1933). (6) Reynolds, P. S., Ross, W. H., and Jacob, L. D., J. Assoc. Oficial Agr. Chem., 11, 226 (1928). (7) Sanchis, J. M., IND.ENQ.CHIM.,Anal. Ed., 6, 134-5 (1934). (8) Smith, H. V., and Smith, M. C., Univ. Aria. Coll. Agr., Tech. Bull. 43 (1932), (9) Smith, M. C., Lanta, E. M., and Smith, H. V., Ibid., 32 (1931). (10) Thompson, T. G.. and Taylor, H. J., IND.ENQ. CHEM.,Anal. Ed., 5, 87-9 (1933). (11) Willard, H. H., and Winter, 0. B., Ibid., 5, 7 (1933). RECEIVED November 14, 1934.
I
N DESIGNATING results involving the use of a centrifugal machine, the force as compared with gravity (relative centrifugal force) should be specified rather than the number of revolutions per minute, which affords but slight notion of the centrifugal stress to which the material has been subjected, Centrifugal force (in dynes) is given by the relation C = 4rWr(= 39.478nf)
wherein n is the number of revolutions per second and r is the radius in centimeters. C is divided by 980 to obtain the relative centrifugal force, as compared with gravity. From inspection of this equation, it may be noted that to secure higher forces it may be expedient to increase the speed of a centrifuge rather than its radius, for centrifugal force varies as the square of the speed and is only directly proportional to the length of the rotating arm. In estimating the volume of precipitates or of living cells ( 4 , 6 ) by the centrifuge, the final degree of compacting is usually a function of (a) the centrifugal force and (b) the duration of centrifugalizing, and unless the speed of the instrument is such that it exceeds the region where ultimate packing has been attained, the measurements should be made a t known forces for comparison of results. The problem of the factors influencing sedimentation rate has been treated by Robinson (6),while a few of the elementary principles governing the use of the centrifuge have been elucidated by Killeffer (3). For ready calculation of centrifugal force, a nomogram is submitted which may be used for laboratory and industrial machines having a radius up to 27 cm. and a speed not exceeding 2000 r. p. s. This makes it available for use with the small high-speed air turbines which have recently come into more general use (1, 2). By stretching a thread between desired values of n (r. p. s.) and r (radius in cm.) the relative centrifugal force may be read off directly from the middle line (RCF). Centrifugal forces found by use of this nomogram are too high, in most regions, by from about 2 to 6 per cent.
JJTERATTJRECITED
i'
(1) Beams, Weed, and Pickels, Science, 78, 338 (1933). Harvey, Bid. Bull. 66, 48 (1934). ENQ.CHEM.,19, 287 (1927). (3) Killeffer, IND. (4) Krueger, J. Cen. Physiol., 13, 553 (1930). (5) Robinson, IND.ENQ.CHIM., 18, 869 (1926). (6) Tang and French, Chinese J. Physiol., 7, 353 (1933). (2)
RBCEIW.D September 17, 1934. Present address, University of Chicago, Chicago, 111. National Research Fellow in the Biological Sciences.
25 23 20 17
5
2
II
io
.5 3.5 3 2.5 2
.7
