Note on the results of cooling certain hydrated platin-cyanides in liquid air

In the course of Sir James Dewar’s important low-temperature researches he made an interesting and significant observation with a salt which had been supplied to the Laboratory of the Royal Institution as “Lithium Platinocyanide.” When this nearly white crystallised substance was cooled in liquid air it assumed a distinctred colour, which did not persist at ordinary temperatures, the material resuming its usual appearance. Sir James was so good as to give the writer a portion of the salt for examination, as it seemed desirable to seek for some explanation of the remarkable colour change observed. On repeating the above-mentioned experiment several times with one and the same portion of Sir J. Dewar’s specimen it was subsequently found that the substance gradually lost the property of becoming red in liquid air, and assumed instead a markedyellow colour, which was retained at ordinary temperatures. This additional phenomenon has also to be explained, as it is presumably connected with that first observed.