194 REV. S. M. JOHNSTON 



Not a few other observers are worthy of mention, and amongst these the following : 

 Hite,* SAKURAi,t Landsbkrger,| Smitz,§ Jonks,|| BiltzJ and Walker and Lumsden.** 



Before the best results can be obtained, one must have the most suitable instrument. 

 Consequently, as boiling-point results have not been satisfactory when water has been 

 used as solvent, almost every observer has designed a special form of instrument. 



When water has been used as solvent, the determinations which have been made 

 from boiling-point data have been principally molecular weights. 



It would seem that aqueous solutions have presented special difficulty. Jones tt 

 says : " It is a misfortune for the boiling-point method that aqueous solutions cannot be 

 used satisfactorily." 



Mv observations were at first directed to find out, if possible, a method whereby 

 this difficulty might be overcome. After experimenting for a considerable time with 

 the older and most recent forms of the Beckmann boiling-point apparatus, and after 

 a careful consideration of several others, I designed a tube of the Jones-Beckmann 

 type, a sketch of which is given in fig. 1. It embraces what experience taught me 

 were the best points in the Jones and Beckmann instruments, with the object of 

 making a series of experiments on the same salt for widely varying concentrations. 



The tube F had two side tubes, G and D, attached, the small tube, G, for the 

 admission of salt pellets with a rubber stopper, and the larger one, D, fitted with a 

 condenser of the Beckmann pattern. The thermometer used was one of Bkckmann's, 

 reading to hundredths of a degree, which passed through a rubber stopper B into the 

 boiling tube. 



Garnets, platinum tetrahedra, and platinum foil were used for filling material, and 

 the thermometer was placed so as to be a little above the filling material, the latter 

 being arranged in what was considered from experience the best possible way. The 

 garnets were placed in the bottom of the tube to a height about one centimetre below 

 the position the thermometer would take up, platinum tetrahedra were then added, 

 it being found desirable to have enough of these to cover completely a cross-section 

 of the tube, when all the tetrahedra were resting on the garnets. A few more of the 

 latter were added, and small pieces of platinum foil placed on top of all, underneath 

 the position the lower extremity of the bulb of the thermometer should take up. 

 The garnets and platinum tetrahedra steadied the ebullition and checked superheated 

 vapour on its way towards the thermometer. A cylinder,;^ P, of platinum foil was 

 pressed down into the garnets a little, and rose, as is indicated in the sketch given, 

 considerably above the surface of the solvent or solution which the tube might contain. 

 This platinum cylinder served two purposes : it warded off radiation and kept the cooled 

 liquid from the condenser from coming into contact with the thermometer before it 



* A m, ' 'A. to. Jowrn., 17, 507. t Journ. Chem. Soc. (London), 61, 989. 



\ Ber. <L r ' lum. Ges., 31, 458. § Ztschr. phys. Chemie, 39, 409 (1902). 



|| Am. Clum. Journ., 19, 581, also 31, 310 (1904). 1" Ztschr. phys. Chemie, 40, 208 (1902). 



** Journ. Chem. Soc., 7:5, 509 MH98). tt Physical Chemical Methods (Jones), p. 31. 

 \X Physical Chemical M,ili<«ls Uoni-;.s), p. 35. 



