Plane suggested another preparation of **f which we used here. 500 ml of 1 M aqueous **f with 1 g **f added are heated in a bomb at 170 ` C for 48 hours. A very fine, gray solid (about 15 g) is formed, water-washed by centrifugation, and dried at 110 ` C.

Differential thermal analysis showed a very small endothermic reaction at 340 ` C and a large endothermic reaction at 470 ` C. This latter reaction is in accord with the reported decomposition of **f. Thermogravimetric analysis showed a weight loss of 1.8% centered at 337 ` C and another weight loss of 10.8% at 463 ` C. The expected weight loss for **f going to **f and **f is 10.6%. Mass spectrometric analysis of gases evolved upon heating to 410 ` C indicated nitrogen oxides and water vapor. The small reaction occurring at 337 ` C is probably caused by decomposition of occluded nitrates, and perhaps by a small amount of some hydrous material other than **f. All subsequent measurements were made on material which had been heated to 375 ` C for one hour. Emission spectra indicated **f calcium and all other impurities much lower. Chromium analysis gave 58.8% Cr as compared with 61.2% theory. However, **f adsorbs water from the atmosphere and this may account for the low chromium analysis and high total weight loss.

The x-ray diffraction pattern of the material, taken with CuKla radiation, indicated the presence of no extra lines and was in good agreement with the pattern of Douglass. Magnetic analyses by R. G. Meisenheimer of this laboratory indicated no ferromagnetic impurities. **f was found to be paramagnetic with three unpaired electron per chromium atom and a molecular susceptibility of **f, where **f. For exactly three unpaired electrons the coefficient would be 3.10. An infrared spectrum, obtained by H. A. Benesi and R. G. Snyder of this laboratory, showed bands in the positions found by Jones.