210 Canadian Record of Science. 



(31.) P. Virginianum, Linn. 



All our specimens of this species were collected in 

 Ontario. Reported from Nova Scotia and Quebec. 



POLYGONELLA ARTICULATA, Meisn. 



Polygonum articulatum, Willd ; Macoun, Cat. Can. Plants 

 Vol. I., p. 409. 



Sand dunes, Point Aux Pins, Lake Superior, 1869. 

 (John Macoun.) Specimens collected by Dr. Richardson, 

 and labelled " Arctic North America," are probably from 

 the same locality. 



A Satisfactory Sulphuretted Hydrogen 

 Generator. 



Nbvil Norton Evans, M. A. Sc. 

 To those who have much to do with general qualitative 

 analysis or with the quantitative determination of metals, a 

 sulphuretted hydrogen generator which is self-regulating, 

 economical, and always ready for use is a desideratum. Of 

 late years there have appeared in various chemical publica- 

 tions suggestions for the construction or improvement of 

 such generators, but most if not all of these still possess 

 one serious defect : when the generator is out of action, the 

 separation of acid and sulphide is effected wholly or in part 

 by the pressure of the gas ; the gas, however, being soluble 

 to a considerable extent in the dilute acid employed, slowly 

 goes into solution and, by the diffusion of this solution 

 through the mass of liquid, the gas finds its way to the air. 

 Thus, there is a continuous though slow disappearance of 

 sulphuretted hydrogen and a corresponding action of the 

 acid on the sulphide. To prevent this, and have a gener- 

 ator which absolutely stops working when not in use, the 

 separation of acid and sulphide must be effected in some 

 other way than by the pressure of the sulphuretted 

 hydrogen. 



Many years ago an excellent apparatus was devised for 

 this purpose by Prof. Clemens Winkler of the Royal Saxon 



