110 Mr T. H. Easterfield, Some observations on  [Oct. 31, 
the neck of the retort, and then surrounded by a freezing mixture 
of ice and salt. The monohydrated sulphuric acid was now poured 
into the retort through a small funnel, and the tubulus closed by a 
well-fitting cork. : 
In order that the gases might be removed from the body of the 
retort as fast as they were formed, a slow current of air, dried by 
calcium chloride and sulphuric acid, was driven through a fine 
glass tube passing through the cork, and dipping beneath the 
surface of the liquid in the retort. The temperature of the water 
in the bath was now gradually raised by a small Bunsen lamp. 
When the temperature had risen to 40°, pink vapours filled the 
retort, and were condensed in the test tube to a mass of radiating 
crystals of a deep red colour. After about half an hour, the test 
tube was removed and another put in its place. The test tube 
which had been removed was wiped round its edge with a clean 
dry cloth, so as to remove any products of condensation which 
might attack the cork. The tube was then corked, and, after 
being wiped free from the water which adhered to its outer 
surface, was placed in the balance-case for ten minutes and then 
weighed. The increase in weight gave the weight of the substance 
condensed in the tube. The tube was now carefully washed out 
with distilled water. The entire contents of the tube were thus 
removed as a pink solution, with the exception of a thin brown 
film (probably oxide of manganese) adhering firmly to the tube. 
The tube was now dried and again weighed, but only in one case 
could an increase of weight, due to this film, be detected. 
To the pink solution obtained by rinsing out the test tube 
with distilled water, 10 cc. of dilute standard oxalic acid solution 
were added, together with a few drops of dilute sulphuric acid. 
The liquid was thus completely decolourized. It was now warmed 
in the water bath to about 60° and titrated back with approxi- 
mately centinormal permanganate. The difference between the 
volume of centinormal permanganate required to oxidise 10 ce. 
of the standard oxalic acid and the volume used in titrating 
back the oxalic acid, to which the contents of the test tube had 
been added, gave the volume of centinormal permanganate equi- 
valent in oxidising power to the contents of the test tube. From 
this the oxidising power, or available oxygen in the distillate, was 
easily calculated. Since the weight of the distillate was known 
the percentage of available oxygen could be found. 
The results were as follows :— 
Toto: Equivalent volume Percentage 
Tube. My eight of of centinormal of available 
distillate. 
permanganate. oxygen. 
A 0055 gm. 6°4 ce. 9:07 
B ‘0067 Us 10°75 
C ‘0065. 4. 11-28 
