STUDY OF THE PHYSICAL CHEMISTRY OF ANAESTHESIA 175 
later from the same bottle will be found to be weak and give a wrong result. The 
way to guard against this is to fill the bottle with mercury up to the neck immediately 
after drawing off, and at once stopper up. Similar devices were employed in all 
dilutions to complete the process out of contact with air. 
The stock solutions were made by direct weighing, by dropping from a fine 
pipette into graduated glass-stoppered flasks ot 25, 50, or 10c c.c. capacity, according 
to the amount required, immediately filling up to the mark with the particular solvent, 
and setting at once upon a slowly rotating disc, driven at such a rate that the chloro- 
form globules have just time to tall through the solution each time the flask is 
inverted. In this way a rapid solution is effected, so saving much time. Furthe^ 
in certain cases such shaking is indispensable, for a solution of haemoglobin left in 
contact with even a small amount of chloroform without continuous shaking soon 
forms a precipitated layer at the bottom. 
The stock solutions were kept carefully stoppered, unless at the moment of 
introducing the pipette to remove a portion for experiment, and then the space within 
the bottle was always filled to the stopper with mercury in the manner above described. 
We found much difficulty owing to leakage of chloroform during dilution in 
the case of the strengths intermediate between the stock strengths, until it occurred 
to us to make these dilutions in the densimeter itself. For this purpose we always 
placed the mercury level at ro c.c. below the stopper on the side of the densimeter 
in which the mixing was to be carried out, then the proper amounts of the two 
solutions necessary to give the desired strength was drawn up in two graduated 
pipettes and run into the densimeter tube, the stopper was then inserted, including 
only a minute bubble of air, and now by thorough agitation of the iron stud through 
the fluid by means of the electro-magnet a thorough mixing of the two fluids was 
attained, then by raising the mercury-holder and slightly easing the stopper 5 c.c. 
were allowed to escape, the mercury level being placed accurately at 5 c.c. A seal 
of mercury was finally dropped in above the stopper, and so the dilution was effected. 
For example, to obtain a dilution of 1-5 per cent., 5 c.c. of one per cent, solu- 
tion and 5 c.c. of two per cent, solution were drawn off into pipettes, placed in the 
densimeter and mixed as above described ; to obtain a 0*4 per cent, solution, 6 c.c. 
of the solvent were taken and 4 c.c. of a one per cent, solution, and similarly treated ; 
to obtain a 0-03 per cent, solution, 7 c.c. of solvent and 3 c.c. of o* 1 per cent, 
solution were taken, and so on. 
Certain of our experiments were carried out at room temperature and others 
approximately at body temperature (40 0 C.) ; the following protocols and accom- 
panying curves show some of the typical results obtained, which have been confirmed 
in most cases by duplicates : — 
Variable Vapour Space 
Experiment I. — Distilled water containing approximately 0^78 per cent, of 
