186 



MR J. Y. BUCHANAN ON THE 



Table I. 



Constants of Hydrometers A and B when loaded so as to Jloat with small 



added Weight, 



(a) In Distilled Water, and 



(b) In a Supersaturated Solution of Calcium Chloride. 



(a) Distilled Water. 



Hydrometer A, 



Hydrometer B. 



Weight of glass ......... grams 



Volume ,, ......... c.c. 



Weight of lead shot used for internal load .... grams 



Volume „ ,, „ .... c.c. 



Weight of the loaded hydrometer as in vacuo . . . grams 

 External volume of hydrometer . . . . . .c.c. 



Internal space occupied by air . . . . . c.c. 



Volume of stem from zero scale division to the top of the stem c.c. 



40-5 



16-2 



95 6 



8-4 



136-1113 



137-09 



112-49 



1-2 



38-11 



15-24 



78-00 



6-87 



115-1026 



118-09 



95-98 



1-0 



(b) SUPERSATDRATED CaLCIUM ChLORIDE SOLUTION. 



Weight of glass ......... grams 



Volume ........... c.c. 



Weight of lead shot used for internal load .... grams 



Volume ,, „ ,, ... c.c. 

 Weight of the loaded hydrometer as in vacuo . . . grams 

 Internal space occupied by air . . . . . . c.c. 



40-5 



16-2 



148-3 



13-1 



188-8312 

 107-79 



38-11 



15-24 

 125-4 



11-05 

 163-5755 



91-80 



The use of these constants in arriving at the volume of air enclosed in the hydro- 

 meter, and in the reduction of the weight of the hydrometer in air to its value in vacuo, 

 has been described in Section XI. 



A little consideration and experience enables the experimenter to adjust the internal 

 load so that the greatest possible range of specific gravity may be covered without 

 altering it. The inferior limit of this range corresponds to a solution of such density 

 that the hydrometer floats in it, immersed up to the highest division in the scale, with- 

 out the addition of any external weight. The superior limit of the range corresponds 

 to a solution of such density that the external weight to be added in order to immerse 

 it to the lowest division on the scale begins to endanger the stability of the hydrometer 

 as a floating body. 



§ 105. Experiments and Observations with Hydrometers A and B. — The first 

 set of determinations of the specific gravity of the supersaturated solution (7 "225 

 CaCl2+ 1000 grams of water) was made on 11th May 1910 in one of the smaller rooms 

 of the Davy-Faraday Laboratory. The room has a northerly exposure, which is 

 essential, and in other respects it is well suited for this class of investigation (§ 24). 



A series of observations had been made with each hydrometer, and further observa- 

 tions were proceeding, when it was noticed that discrepancies between successive 



