IV. On the physical constants of liquid hydrochloric acid

In a paper read before the Royal Society, on June 18th, 1879, I described the results of some experiments made with liquid acetylene, obtained by compressing the gas in one of M. Cailletet’s ingenious pumps for the liquefaction of gases. The tensions of the saturated vapour then obtained were so entirely different from M. Cailletet’s results, that it appeared to me to he possibly due to a slight impurity in the gas, probably a trace of mono-bromethylene which always occurs in the red copper compound of acetylene, and is very difficult to completely eliminate. I therefore prepared a quantity of the silver compound (which can be obtained entirely free from mono-bromethylene) by passing acetylene prepared in the same way as formerly, viz., by the action of alcoholic potash on di-bromethylene, into an ammoniacal solution of nitrate of silver.