326 THE EARL OF BERKELEY, MESSRS. E. G. J. HARTLEY AND C. Y. BURTON: 
A word of explanation is necessary ; all weighings are made against a sealed 
counterpoise which is constructed of the same material as the vessels, and has 
approximately the same area exposed to the air. The counterpoise and vessels are, 
before weighing, treated with “ chromic ” acid, washed carefully with distilled water, 
and finally with pure alcohol. The alcohol is wiped off with linen dusters. It is hoped 
that this procedure results in leaving the surfaces in the same condition. The letters 
It and L mean that the counterpoise is on the right or left pan respectively, and the 
small correcting terms are those due to buoyancy. 
The results obtained for these two substances are given in Tables VIII. and IX., 
and it should be mentioned that in all the tables relating to vapour pressure, columns, 
which are numbered the same, tabulate corresponding quantities. 
Column (l) gives the date of setting the apparatus up in the bath and starting the 
air current. 
Column (2) gives the weight concentration of the solutions, that is the ratio of 
number of grammes of anhydrous substance to 100 gr. of water. 
Column (3) gives the mean temperature* of the bath during the experiment ; and 
Column (4) the mean barometer. It was only after the experiments at 0° C. were 
finished that the importance of Burton’s correction was discovered. Although the 
height of the barometer had not been noted we were able to estimate the mean baro¬ 
metric pressure to an accuracy of 1 mm., from the records of a large-size aneroid baro¬ 
graph which is part of the laboratory equipment. Where by some mischance the 
barograph has failed, the barometer readings were kindly supplied by the Director of 
the Badcliffe Observatory at Oxford, to whom our best thanks are due. 
Column (5). The numbers in this column are the total loss of .weight of solution and 
solvent vessels ; ii t the earlier part of the research we filled all solution vessels with 
the same solution ; later work showed that two different solutions in series might be 
used, and the numbers marked thus t indicate these experiments. The numbers are 
the observed values corrected for buoyancy. 
Column (6) gives the sum of the observed losses of weight of the solution and 
water vessels divided by the loss in the solution vessels, i.e., the ratio ljl v 
Column (7) gives the change in weight in the inverted U-tube (“dipping’’ tube) 
connecting the water and sulphuric acid vessels. This tube was always weighed as 
soon as possible after disconnecting the vessels ; in most experiments with Apparatus 
Aa a trace of dew,| which quickly disappeared, was noticed on the outer surface of 
the part of the tube next to the water. A minus sign means that the tube lost 
weight on passing warm air through it ; a positive sign can only be the result of 
* In the cases where this quantity is enclosed in brackets it is to he understood that owing to some 
slight mishap the experiment is not as trustworthy as others. 
J Probably the dew (it was seldom observed with the other apparatus) is caused by the cooling of the 
air stream, when throttled by having to pass through this tube, which is slightly less than 1 mm. in 
internal diameter. - --- 
