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The Assimilation of Fluorine by Rats from Natural and Synthetic Cryolite and from Cryolite-Sprayed Fruits^1,2,

Division of Animal Nutrition, University of Illinois, Urbana

Four experiments have been performed on growing rats, involving the controlled feeding and chemical analysis of twenty-four trios and twenty-four pairs of animals. These experiments were designed to detect and measure differences in retention by animals of the fluorine in natural Greenland and domestic synthetic cryolite and possible modification of such retentions by the particle size of mineral, by the weathering of spray chemicals on the fruit and by the development of the wax coating on the surface of sprayed apples.

The results obtained appear to warrant the following conclusions:

1. The fluorine of synthetic cryolite is appreciably more completely retained by animals than the fluorine of natural cryolite, probably a result of the greater solubility of the fluorine contained in it.

2. The degree of fineness to which cryolite is ground may modify the assimilation of the contained fluorine.

3. The weathering of natural Greenland cryolite on sprayed fruit does not appreciably affect its assimilability by animals nor presumably its toxicity.

4. On the other hand, with synthetic cryolite, weathering on the fruit will in some degree lower the assimilability of its fluorine, conceivably by leaching out some, or all, of the more soluble compounds of fluorine contained in it. Thus, the differences observed between synthetic and natural cryolite tested in an unweathered form will tend to disappear when the two cryolites are applied to fruit in spray mixtures and subjected to weather conditions.

5. Possibly the development of a wax coat on apples sprayed with cryolite impairs the assimilability of the contained fluorine, as it seems to render more difficult the removal of spray residue by commercial washing. The experiments reported in this paper relating to this subject, while not particularly assuring in support of this conclusion, quite probably did not permit the full effect of waxing to be exerted.

² This investigation was conducted under the general supervision of a Committee on the Physiological Effects of Spray Chemicals, appointed by the Director of the Agricultural Experiment Station and consisting of the following members: H. H. Mitchell, W. A. Ruth, W. P. Flint and Julia P. Outhouse.

Manuscript received 30 June 1941.