Calcidin is a bluish black powder having the odor of iodin. Extracted with water, a clear colorless solution is obtained and a white residue remains. The residue treated with acids liberates carbon dioxid abundantly. A microscopic examination of this residue shows the presence of corn starch in large quantities. The solution, when acidulated, liberates iodin. When calcidin is charred a residue remains which is soluble in hydrochloric acid, and contains traces of iron and aluminum, large quantities of calcium and some magnesium. Iodin.—Total iodin (a), 1.3933 gm. calcidin was mixed with a solution of 1 gm. potassium hydroxid in 10 c.c. water, evaporated to dryness and ignited. The residue was extracted with small portions of hot water, using in all about 75 c.c., filtered, and the filtrate collected in a separator. When cool 10 c.c. hydrochloric acid was added, followed by 10 c.c. solution of ferric chlorid U. S. P. When, after standing one-half hour, the liberated iodin was extracted with carbon disulphid and titrated with tenth-normal sodium thiosulphate V. S., 15.25 c.c. were required, indicating 0.1920 gm., or 13.78 per cent. iodin. (b) 1.2079 gm. calcidin was fused with potassium hydroxid as outlined above. The residue was dissolved in water by the aid of nitric acid and the liquid filtered. In the filtrate the total halogen content was determined by precipitation with silver nitrate and calculated as silver iodid. 0.3197 gm. silver halide was obtained, equivalent to 0.1727 gm., or 14.3 per cent. iodin. In a duplicate determination 1.2214 gm. calcidin gave.3236 gm. silver halide, equivalent to.1748 gm., or 14.31 per cent. iodin. Average: 14.13 per cent, total iodin. Available Iodin.—Iodin liberated on acidulation was determined as follows: (a) A weighed quantity of calcidin was added to 50 c.c. water and acidulated with hydrochloric acid. The liberated iodin was then titrated with tenth-normal sodium thiosulphate V. S., using as indicator the blue color of the starch iodid present. The end point was not sharp and an excess of the thiosulphate V. S. seemed to be necessary to completely destroy the color. Varying results were obtained, averaging about 9.75 per cent, free iodin. This being unsatisfactory, the following method was finally adopted as giving the best results. (b) 0.7838 gm. calcidin was washed by decantation with small portions of water, filtering each portion and continuing the washing until the filtrate gave no reaction with silver nitrate T. S., and the residue was white. The solution was acidulated with hydrochloric acid and the iodin set free determined with tenth-normal sodium thiosulphate V. S.; 5.73 c.c. were required, indicating.0721 gm., or 9.2 per cent. iodin. In a duplicate determination.7049 gm. calcidin required 5.15 c.c., indicating.0648 gm., or 9.2 per cent. iodin. Average, 9.2 per cent, available iodin. Calcium.—(a). 1.3710 gm. calcidin was ignited to expel iodin and to destroy starch. The residue was dissolved in hydrochloric acid, and after removal of iron and aluminum the calcium was precipitated as calcium oxalate, and weighed as calcium oxid. Found.5325 gm. calcium oxid, indicating 27.76 per cent, calcium (Ca). In a duplicate,.5902 gm. calcidin gave.2295 gm. calcium oxid, indicating 27.78 per cent, calcium. Average: 27.77 per cent, calcium. (b) Calcium was converted into calcium sulphate by direct ignition of calcidin with sulphuric acid. 0.3497 gm. calcidin gave a residue weighing 0.3405 gm., indicating 28.67 per cent, calcium. In this determination the traces of iron, aluminum and magnesium were weighed as calcium sulphate. For this reason the result is not considered in calculating the composition of calcidin, but is included as confirming the estimation under the first method and as demonstrating the absence of appreciable quantities of alkali metals. Magnesium.—Magnesium was determined in the filtrate from the calcium oxalate precipitation. After evaporating to dryness and igniting to expel ammonium salts, the residue was dissolved in dilute hydrochloric acid and filtered. In this filtrate, magnesium was determined in the usual way. 1.371 gm. calcidin gave 0.016 gm. magnesium pyrophosphate, indicating.21 per cent, magnesium (Mg). Carbon Dioxid.—Carbon dioxid was determined by the aid of Knorr's apparatus as outlined in U. S. Department of Agriculture, Bureau of Chemistry Bulletin, No. 65, p. 98. The apparatus was modified by placing between the condenser and the bulb containing the sulphuric acid a calcium chlorid tube charged with sodium sulphite. This was found necessary to absorb iodin carried over when the solution was heated to expel carbon dioxid. 1.8068 gm. calcidin gave.277 gm. CO2, indicating 15.32 per cent, carbon dioxid. In a duplicate, 1.9869 gm. calcidin gave.2985 gm. CO2, indicating 14.98 per cent, carbon dioxid. Average: 15.15 per cent, carbon dioxid. Starch.—The starch was estimated by treating 1.1098 gm. calcidin with small portions of cold water until all iodin was removed. The lime was next removed by washing with very dilute hydrochloric acid. The insoluble residue collected on a weighed filter and dried to constant weight, weighed.1790 gm., indicating 16.13 per cent, starch. In calculating the probable composition of the powder from the above analysis, it was assumed that the iodin, which is not liberated when dilute acid Is added, is present as calcium iodid, that a part of the calcium is in combination with the carbon dioxid, and that the remaining calcium is present as calcium oxid or calcium hydroxid. The presence of such a large per cent, of carbon dioxid would seem to indicate that the lime had been decomposed by exposure to air or otherwise. Therefore, the calcium not present as calcium carbonate or iodid is probably present as calcium hydroxid. Following the usual custom, it is calculated to calcium oxid, however, as is also the magnesium. The water present as water of hydration and also that normally contained in the starch is reported as "difference." The analysis shows that the specimen of calcidin contained: Per cent. Iodin (I).... 14.13 Calcium (Ca).... 27.77 Corn starch (anhydrous).... 16.13 Magnesium (Mg).....21 Iron and aluminum.... Traces Carbon dioxid (CO2).... 15.15
A one-ounce package of 1/3 grain calcidin tablets was purchased in the open market and the available and total iodin content of the tablets determined. "Available" Iodin.—The method of estimating available iodin adopted in the analysis of calcidin did not work because of difficulty in filtration, and method (a) was used. Fifty tablets were triturated with water, the mixture was acidulated with hydrochloric acid and the liberated iodin determined with sodium thiosulphate. The end point was not sharp, but less than 1 c.c. of tenth-normal sodium thiosulphate V. S. was consumed, equivalent to.01259 gm. iodin; hence each tablet contains not more than.00025 gm. (1/250 grain) "available" iodin. Total Iodin.— (a) Fifty tablets were fused with potassium hydroxid. The residue, treated as outlined for the estimation of total iodin in calcidin, required 12.2 c.c. tenth-normal sodium thiosulphate, V. S., indicating.1536 gm. iodin, or.0030 gm. iodin per tablet. (b) Fifty tablets were mixed with 2 gm. potassium hydroxid and 5 c.c. water, evaporated to dryness and ignited. In this residue the total halogen content was determined gravimetrically, as outlined under calcidin..2857 gm. silver halide was obtained, In-indicating.1544 gm. iodin. or.0031 gm. per tablet. In a duplicate determination, 50 tablets gave.2764 gm. silver halide, indicating.1493 gm. iodin, or.0031 gm. per tablet. Since each tablet contains.0030 gm. total iodin (average of the three estimations), and liberates on acidulation.00025 gm. iodin, the difference,.00275 gm. iodin, Is probably present combined with calcium as iodid. This indicates about 0.0031 gm. (1/18 grain) calcium iodid per tablet.