1877.] 



On the Density of Solid Mercury. 



71 



In iny paper before referred to it was suggested that, " considering 

 the stability and mode of formation of these bases, it is not at all im- 

 probable that they may be produced by the simultaneous action of 

 acetylene and its derivatives on hydrocyanic acid ; thus as three mole- 

 cules of acetylene condense and form benzol, so may two molecules of 

 acetylene and one of hydrocyanic acid condense and produce pyridine." 



A synthetical experiment of the kind suggested has been executed by 

 Mr. Kamsay*, who finds that by transmitting a mixture of acetylene and 

 hydrocyanic acid through a red-hot tube bases were unquestionably pro- 

 duced. Pyrrol, which may be so readily identified by means of its 

 characteristic reaction with fir wood moistened with hydrochloric acid, 

 maybe formed synthetically by substituting ammonia for the hydrocyanic 

 acid in the above experiment. The acetylene employed, however, con- 

 tained a small quantity of bromide of vinyl, and it is possible the reaction 

 may have taken place between that substance and ammonia. Only a 

 small quantity of pyrrol is formed in this reaction, the principal sub- 

 stance formed being cyanide of ammonium ; and the success of the ex- 

 periment seems to depend on the maintenance of a carefully regulated 

 temperature and a certain extent of porous surface. These and similar 

 reactions are under investigation. 



The theoretical bearings of this investigation have not been touched 

 upon in the present paper, as an extensive research will be necessary 

 before structural relations can be predicted with any certainty. 



I am greatly indebted to Mr. "W. F. Sell, B.A., and Mr. A. Scott, B.Sc, 

 assistants in the Chemical Department, for aid in the course of the 

 investigation. 



Laboratory, Cambridge University. 



III. « On the Density of Solid Mercury By Prof. J. W. Mal, 

 let, University of Virginia. Communicated by Prof. Stokes, 

 Sec.R.S. Received February 22, 1877. 



I have lately taken advantage of a heavy fall of very cold and finely 

 pulverulent snow, well adapted to the preparation of freezing-mixtures, 

 to redetermine, with accuracy I believe, the density of mercury in the 

 solid state and at a definite temperature. 



Such redetermination was not superfluous, as appeared from a coDa- 

 tion of the statements to be found in various standard works. In the 

 tables of specific gravities compiled by Prof. P."W. Clarke, and published by 

 rhe Smithsonian Institution t, there are four authorities quoted, with the 

 numbers given by these, as follows : — 



* "On Piooline and its Derivatives," Phil. Mag. 1876, vol. ii. p. 269. 

 t " The Constants of Nature. — Part I." Smithsonian Miscell. Coll. 255, Washing- 

 ton, 1873. p. 24. 



