STRUCTURE AND DYNAMICS OF CRYSTALLINE C60·n-PENTANE CLATHRATE

Clathrate type single crystals with the composition of C 60(n- C 5 H 12)0.88( C 7 H 8)0.05 were grown from C 60-toluene-petroleum ether solution. The structure of the crystals, determined by X-ray diffraction is b-face centered orthorhombic. A phase transition is observed at 190 K by differential scanning calorimetry.

Some factors affecting determination of carotenoids in serum.

Because of increasing interest in carotenoid pigments, we conducted a study of the methods of determining carotenoids in serum. We found 1 mol of KOH per liter of absolute methanol to be the most effective saponifying solution. The absorbance of beta-carotene in petroleum ether, the extraction solvent, is proportional to dilution up to an absorbance of 0.85 at 450 nm. Beta-carotene in petroleum ether solution is not impracticably sensitive to ambient light at room temperature. However, if vitamin A is also to be measured in these serum specimens or petroleum ether extracts, exposure to light should be minimized. We found that serum may be shipped either in cold packs or at ambient temperature (tested up to five days) without significant change in carotenoid concentration. Serum samples for carotenoid determination are best stored at -70 degrees C: samples stored at -20 degrees C deteriorate substantially over several months.

Modifications of the Gutta-Percha Hydrocarbon

The spongy product from gutta-percha hydrocarbon, which is obtained from a concentrated petroleum ether solution, consists of microcrystals of the α-modification. The difference in its solubility and that of the compressed product prepared from the spongy product is perhaps attributable to the presence of an impurity. By treatment of the fused hydrocarbon with benzene below 19° C. both the β-form and the amorphous form dissolve, and one of these forms is converted, or perhaps both of the forms are converted, into the α-form. It is possible that petroleum ether dissolves not only the amorphous form but also a part of the β-form. It does not, however, transform the β-form into the α-form. Compression in the cold of previously fused strips, as well as of strips elongated while cold, decreases the solubility of these strips in benzene below 19° C. Cold-drawing of threads, which have been prepared from fused products, has only a slight influence on the stability of the threads in benzene below 19° C.