82 THE ROYAL SOCIETY OF CANADA 
(b) Failure to get over the last traces of emanation, owing to 
its remaining in the delivery-tube and escaping into the room on 
second boiling. 
(c) Bad rubber tubing, accounting for the extremely low readings. 
(d) Temperature changes from the coils. 
(e) Possible irregularity in the time recorded by the stop-watch, 
due to faulty mechanism. 
It was also decided as a precaution to use a Kjeldahl trap. This 
effectively prevents any of the radium solution from being driven 
over into the collecting-apparatus by too vigorous boiling: any that 
may be shot up into the bulb falls back again into the flask. 
The results of these investigations were now acted upon, and the 
results showed a marked improvement. The second solution of 
Rutherford—Boltwood II, had to be discarded owing to some of the 
solution being lost through tube-burst in boiling. 
An interesting development in the course of the latter part of 
this work is that there seemed to be no deterioration with boiling. 
This was first evident through all the solutions of the same kind 
having values in close agreement. It was finally settled by taking 
Washington III, which had been also made up in August, 1915, and 
never boiled. This one was first boiled, the emanation discarded and 
the flask sealed up. It was then boiled off at intervals of a week or 
more and the results obtained show them extremely close (see below) 
to those got for the other two preparations of the same standard 
which had been boiled off ten or twelve times. This not only gives 
consistent results for the standards, but settles the question of boiling. 
The readings of Washington III do not differ enough from I and If 
to warrant the conclusion that boiling causes deterioration. The 
apparent diminution of strength with boiling noticed in previous 
work must therefore have been due to lack of refinements in the 
apparatus and technique, such as have been investigated and sum- 
marised in this paper in a previous paragraph. 
The following are the tables of results obtained: 
