186 
in solution, is an index to the amount of pollution by sewage 
and manufacturer’s waste waters. The water of the River 
Irwell is almost saturated with carbon dioxide gas at the 
temperature of the air. I have often proved that this carbon 
dioxide gas must be derived from the organic matters in the 
water, by determining the amount of dissolved carbon dioxide 
in a sample, and then keeping the same sample for several 
weeks, and ascertaining how much of the gas was dissolved 
in it, at intervals of a week, with the same result in all cases, 
viz : — a further increase in the amount of carbon dioxide 
gas dissolved in the water. This proves that the organic 
matter is easily decomposed into gaseous products, conse- 
quently it becomes a great difficulty how to ascertain the 
total organic carbon in a sample of polluted water. 
About August, 1884, I first applied a slight modification 
of Ulgren’s well-known method for determining the amount 
of carbon in steel, to water analysis. 
The process is as follows : 
Take an eight oz. or twelve oz. flask, fitted with a syphon 
funnel tube passing to the bottom of the flask, a thermo- 
meter, and an exit tube passing out of the flask into the 
bottom of a 4 oz. flask containing 50 c.c. of a standard solu- 
tion of calcium hydrate, and an exit tube from this last 
flask passing to the bottom of another 4 oz. flask, also con- 
taining 50 c.c. of calcium hydrate solution. The exit tube 
from this last flask is connected with a small tube containing 
small pieces of caustic soda, to absorb any carbon dioxide 
gas which might otherwise get into the calcium hydrate 
flask from the air. 
Place in the large flask 250 c.c. of the water sample, 
connect all the flasks, and fill partially the funnel tube 
with water, so that the pressure of the air at the end 
of the apparatus is overcome, and sucking back pre- 
vented. Now surround the flask with a water bath, and 
