Viscosities of C cesium Salts. 13 



The viscosities of mixtures of water and formic acid, on the other 

 hand, fall almost on a straight line. This, again, is just what would be 

 expected, from the fact that neither solvent alters appreciably the 

 molecular weight of the other. 



These results are, then, all in keeping with the suggestion made by 

 Jones and Veazey, that the increase in viscosity which results when 

 associated liquids which diminish each other's association are mixed, is 

 due to the larger number of smaller parts that are present. 



These results are in perfect accord with their suggestion as to the 

 cause of the diminution in the viscosity of water produced by salts 

 whose cations have very large ionic volumes, such as salts of potassium, 

 rubidium, and caesium. 



SOME NEW FORMS OF APPARATUS. 



A SUBSTITUTE FOR THE TWIN-BULB TRAP IN TOLUENE-MERCURY 



THERMO-REGULATORS. 



Toluene, on account of its high coefficient of expansion, is to be pre- 

 ferred to all other liquids for use in thermo-regulators. Since, however, 

 it is practically a nonconductor and quite volatile, it is ordinarily used 

 with mercury for the contact in all electrically operated thermostats. 



In order to use these two liquids together, the common form of appa- 

 ratus hitherto employed has been the twin-bulb device, which, however, 

 has the following disadvantages: 



1. It is very fragile and can only be made by an expert glass-blower. 



2. When the mercury level in the capillary has been once adjusted 

 for any given temperature and the toluene reservoir sealed, the regu- 

 lator is practically useless for any higher temperatures without opening 

 the reservoir and removing the excess of toluene in order to preserve 

 the equilibrium in the two bulbs. 



3. It is difficult to prevent the toluene from finally creeping around 

 between the mercury and the glass walls into the capillary and fouling 

 the contact surface of the mercury, since the same continuous tube 

 contains both the toluene and the mercury. 



To overcome these difficulties as far as possible, the apparatus 

 illustrated in figure 3 has been devised. This consists of a bulb a 

 attached at the bottom by the tube 6 to the toluene reservoir, which 

 may be of any desired form. Exactly opposite to & is a corresponding 

 tube (c), which carries the capillary and sealed-in platinum contact. 



The interior construction of a is as shown in the figure. The small 

 tubes e and / are prolongations of c and b, respectively, having a length 

 nearly equal to the diameter of the bulb. These tubes are inclined at 

 an angle of about 30 to the perpendicular. The short side tube d is 

 used in filling the regulator and is in exact alinement with /. 



To prepare the regulator for use, mercury is poured in through the 

 capillary until the bulb a is from one-half to three-fourths filled. A 



