308 report — 1879. 



Pfaundler's method, of which a preliminary notice appeared in 1870, but 

 which was not brought prominently forward till this year, is based on the increased 

 tension of the air in an elongated bulb produced by heating after the introduction 

 of the substance, as compared with a similar determination of air in a bulb of the 

 same size. A very short description appeared in 1874 of a method devised by 

 Dulong, which is based on the same principle. 



Last year Hofmann proposed two methods ; in one of these, he heated the 

 weighed substance over mercury in the closed limb of an U tube, and marked the 

 level of the mercury in the open limb by sliding a pointed tube through a loosely- 

 fitting perforated cork until it touched the surface. When the apparatus was cool, 

 the volume of the vapour was calculated from the weight of mercury required to 

 restore the level to that same point. The other consisted in introducing into a 

 tube a small but weighed quantity of substance, then exhausting it, and sealing it, 

 and heating in a jacketed tube. At the required temperature, the point of the 

 glass tube is opened to allow air to enter, and then at once sealed again. After 

 cooling, the point is opened under mercury or water, and the volume occupied by 

 the vapour is measured. 



In Meyer's method, which is so recent and well known as not to require any 

 explanation, the principle is that of Pfaundler's, but by having the neck elongated, 

 and the outlet as a side-tube, the substance is introduced after the bulb is heated 

 to the required temperature, and by allowing the air expelled by the vapour free 

 egress into a graduated tube, it can be measured under atmospheric conditions. 

 It is, therefore, so simple that the operation only requires a very short time from 

 first to last. 



In this sketch I have purposely kept off the very enticing ground of formula, 

 as they, of themselves, open up so wide a field that they could not be dove-tailed 

 into the history of the subject, which from any point of view is interesting. 



6. Note on the Vapour Densities of Ferrous Chloride and Iodide of Potassium. 



By J. Alfred Wanklyn. 



The recent "observations made by the method of Victor Meyer admit of expla- 

 nation on the supposition that ferrous chloride, when strongly heated in an iron 

 vessel, is resolved into Fe 2 01 2 , and that the iodide of potassium, under like con- 

 ditions, give3 K 2 + Fe 2 1 2 . 



7. Note on the Constitution of Isocyanopropionic Acid. 

 By J. Alfred Wanklyn. 



In the ' Philosophical Magazine ' for last May, Mr. Cooper and myself described 

 an acid to which we gave the name isocyanopropionic acid. 



The acid had been prepared by the oxidation of wool by means of perman- 

 ganate of potash and caustic potash, and had the formula C,H 5 N0 3 . 



We have acted upon the acid by means of caustic potash at 200° 0., and 

 thereby obtained ethylamine and oxalate of potash, thus : — 



4 H 5 NO 2 + 2KHO = C 2 K 2 4 + 2 H 7 N. 



This reaction points to the following structure : — 



HO CO 

 O 



N 



CH 

 OH 3 , 



and the acid should therefore be called ethylene-isocyan oxalic acid. 



It is no doubt the representative of a numerous class of acids, characterised 



