~~~
used, new standards had to be made up. I n addition, possibly because the particles of color lake were smaller than those of the Icken and Blank reagent, bleaching by fluoride took place more rapidly and readings could be made a t once, or after a delay of several hours, whichever was more convenient. If the color reagent and standards were prepared beforehand, it was possible to complete an entire fluoride determination in from 0.5 to 1 hour. An additional advantage of the buffered color reagent was that standards prepared from it gave a straight-line curve in the range from 1 to 10 y per ml. when absorbance was plotted against concentration (Figure 2). When the Icken and Blank reagent was used, the type of curve reported by these authors was usually found, although occasionally a straight-line segment would be obtained up to about 5 y of fluorine per 10 ml. The data of Table I11 are typical of the results obtained when the method was applied to bone and tooth samples. The values for cartilage do not indicate the presence of any fluoride. The values for the dentin samples indicate barely detectable amounts. LITERATURE CITED
(1) Armstrong, W. D., IND.ENG.CHEM., ANAL.ED. 8, 384 (1936). (2) Armstrong, W. D., Univ. of Minnesota Medical School, Minneapolis 14, Minn., personal communication.
(3) Bien, S. M., J. Dental Research 22, 123 (1943). (4) Gilkey, W. K., Rohs, H. L., Hansen, H. V., IND.ENG. CHEM.,ANAL. ED.8,150 (1936). (5) Hoskins. W. M.. Ferris. C. A.. Zbid., 8 , 6 (1936).
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Table 111.
Analysis of Bone and Tooth Samples for Fluorine
Sample Cattle bone
Sample Wt., Mg. 20.40 11.60 25.00 25.00 50.00 50.00 27.68 15.23 25.00 25.00 50.00 50.00
Rat bone (diaphysis)a Rat bone ( ~ a r t i l a g e ) ~
2.89 2.86 2.81 2.02
Fluorine, y Added Found 4.3 2.3 5.7 5.2 10.5 10.8 3.0 8.6 4.0 7.4 5.0 10.4 5.0 10.7 10.0 21.8 10.0 20.8 7.5 9.0 0.3 0.3
% F in Sample 0.021 0.019 0.023 0.021 0.021 0.022
F Recovered, Y
3.1 4.4 4.9 5.2 11.1
10.1 0.26 0.31
