154 Dr. J. A. Barker. 



(1) That the effect which ether-oxygen exerts on the viscosity of 



a liquid differs to a marked extent from the effect exerted 

 either by hydroxyl-oxygen or carbonyl-oxygen, and thai 



(2) The viscosity of the formate is abnormally large when com- 



pared with that of other esters, and indicates that the 

 exceptional behaviour of formic acid is to some extent 

 retained by its ethereal salts. 



" On the Determination of Freezing Points." By J. A. HARKER, 

 D.Sc. Communicated by Professor SCHUSTER, F.R.S. Re- 

 ceived June 15, Read June 18, 1896. 



(Abstract.) 



Of recent years great improvements have been made in the con- 

 struction of accurate thermometers. For their graduation and study, 

 the position of the thread for at least two fixed temperatures must 

 be known with certainty, and one . of these is generally the freezing 

 point. According to many observers, the methods at present in use 

 for the determination of this point are unsatisfactory and cannot be 

 relied on, even when considerable precautions are taken, to more 

 than about 0*001 to 0'002. The object of the present communica- 

 tion is to describe a method by which more consistent results can be 

 obtained, and which is applicable to all kinds of thermometers. 



The method adopted is to cool distilled water in a suitable vessel, 

 protected from radiation, to a temperature below 0, to insert the 

 thermometer, and then bring about the freezing of the water by 

 dropping in a crystal of ice. The thermometer then rises, and 

 finally attains a steady temperature, differing only very slightly from 

 the true zero. 



Within the space allotted to this abstract, it is not possible to 

 describe in detail all the precautions to be adopted and the apparatus 

 employed, and for these reference must be made to the original 

 paper. The following brief outline may, however, be given. 



The apparatus consists of two portions, the thermostat and the 

 cooler. The former is a rectangular copper vessel, filled with some 

 liquid, which can be cooled below without solidifying. 



Generally either refined petroleum or a strong solution of common 

 salt is employed. This vessel communicates by means of two wide 

 tubes with a system of coils in the cooler, through which the liquid 

 can be pumped by a rotary stirrer. These coils are surrounded by 

 a freezing mixture at about 8, and by this means the circulating 

 liquid can be cooled and maintained for some time at about 2. 

 The distilled water to be frozen is contained in a tube of about 

 300 c.c. capacity made of clear glass. This is first placed directly 



