Potassium and sodium-potassium eutectic dissolve slightly (of the order of lo-* g.-atom/l.) in certain ethers to give unstable blue solutions which are considered to be similar to the well-known blue solutions of alkali metals in ammonia and amines. Absorption spectra of the solutions show maxima a t about 7000 A.An attempt has been made to correlate the ability to give a blue solution with the structure and basicity of the ethers.IT has previously been reported that moderately stable blue solutions of potassium and sodium-potassium alloy in some ethers may be obtained. Solubility has since been observed in some fifteen ethers and one amino-ether. The solutions are immediately decolorised by air but they can be filtered through a sintered-glass disc in VIECZCO. Filtered solutions decolorise at room temperature, rapidly in some cases and slowly in others, owing principally to attack on the solvent by the alkali metal. The nature of the decomposition products has not been investigated. Generally, the total alkali-metal concentration appears €0 increase with decrease in temperature; in some ethers, viz., the dimethyl ethers oi polyethylene glycols, the surface of the sodium-potassium alloy exhibits a coppercoloured lustre at low temperature, presumably on account of the formation of alkali-metal Down, Lewis, Moore, and Wilkinson, PYOC. Chem. Soc., 1957, 209 (where references t o previous work with water and alcohols are given). EXPERIMENTALAs the solutions were unstable to air they were handled in vacuo or in oxygen-free nitrogen, methods similar to those described previously 8 being used. Preparation and Purification of Materials.-Solvents.Several ethers were available commercially. Others were prepared from available hydroxy-compounds by the Williamson method. The products were fractionally distilled, freed from alcohols by refluxing them over sodium, and distilled from lithium aluminium hydride in a stream of nitrogen.The cyclic tetramer of propylene oxide was prepared by polymerisation with boron trifluonde-ether complex, according to a method kindly provided by Mr. W. J. Toussaint of Union Carbide Chemicals Co., which is as follows: Dry propylene oxide (2198 g.) was added to a flask equipped with a stirrer, a brine-cooled condenser, and a feed tank for catalyst addition. The

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A correlation of molecular flexibility with ring size is also possible in both types of ethers I11 and IV. Compounds V, VI, and VII, which differ only in number of ring difluoromethylene groups (from four-to six-membered rings), vary in order of 0°F. viscosity in ring-size order of 6 >> 4 > 5. The same relationship in the Type IV ethers establishes the better fluid properties of perfluorinated cyclopentane and cyclobutane systems over cyclohexane systems.The thermal stabilities of most of these ethers averaged about 500°F., although V and VI1 ethers had stabilities above 550" F., with the high fluorine content of both ether types resulting in good fire resistance properties. The perfluorocyclobutene trimer, XV, was an extremely mobile fluid with a viscosity of 117 cs. a t -65"F., compared to the acyclic n-CI2Fz6, which is a solid a t 167" F. The thermal stability of XV was above 900" F., as measured by a pressure isoteniscope.

The mass spectra of a number of phosphorus-bridged metal carbonyl compounds and some of their derivatives have been measured. Fragmentation schemes have been established and where possible correlated with structure.