proceedings: chemical society 131 



of health resorts usually arises from other causes than the composition 

 of the water. The reactions of substances usuall}'" present in the min- 

 eral waters are those of the positive or negative salt radicals. Their 

 effect can therefore be predicted by the experimental use of single pure 

 salts in solution at known concentrations. The following phenomena 

 interfere with simple deduction from such experiments: (1) cumulative 

 effects of certain radicals; (2) "toleration" acquired against certain 

 radicals; (3) "interference" of different radicals in the same water. 

 Examples of very concentrated waters in common use in the West were 

 cited, to show that waters having concentrations well above the nor- 

 mally active physiological dose could be used for years with no appre- 

 ciable effect. 



F. C. Cook, of the Bureau of Chemistry: A comparison of plant, meat, 

 and yeast extracts. The paper was concerned largely with methods, and 

 can not be briefly abstracted. 



Discussion: Alsberg suggested that removal of ammonia or presence 

 of some unrecognized compound would result in better agreement be- 

 tween the Van Slyke and Soerensen methods for hydrolyzecl proteins. 

 M. X. Sullivan discussed the presence of small amounts of creatinin in 

 plants, probably too small to affect the test for distinguishing plant from 

 meat extracts. E. C. Franklin also discussed the paper. 



A. S. CusHMAN and E. B. Wettengel of the Institute of Industrial 

 Research: The electrolytic determination of tin in canned food products. 

 Read by Mr. Wettengel. The usual gravimetric method for tin is 

 tedious and expensive. The electrolytic method is much simpler and 

 shorter and was shown by thoro tests to give reliable results. The 

 pulped material is digested with acid, neutralized with ammonia and 

 ammonium sulfide, freed from insoluble matter, and electrolyzed hot, 

 using a rotating cathode. Discussion by Taber and Smith. 



A. Seidell of the Hygienic Laboratory and F. Fenger of Armour and 

 Company: Seasonal variation in the iodine content of the thyroid gland. 

 Reacl by Seidell. A parallelism exists between the iodine content and 

 the physiological activity of commercial thyroid as used in medicine. 

 A standard commercial concentration of 0.2 per cent has been recom- 

 mended. In order to obtain data upon the raw material used in manu- 

 facturing commercial desiccated thyroids, and to study the possibility 

 of meeting such a standard, Mr. Fenger collected samples at Chicago 

 from sheep, hogs, and cattle at two-week periods, each representing 

 about 300 animals. Maxima of iodine were. found in all three between 

 September and November, and minima in summer. A rather variable 

 ash content was found due to the wear of the ball mills. 



Discussion: Waters suggested that the iodine content varied with 

 the amount of green food. Seidell believed tliis was not the only cause 

 of variation. Dole suggested a geographical variation, which was ad- 

 mitted as a possible explanation in spite of the large number of samples. 

 Alsberg added further evidence of a geographical variation. Bunzel 

 quoted the determinations of Koch to show a seasonal variation. Dole 



