187 
heat the water in the flask to about 94°Q, when the dissolved 
carbon dioxide is at once evolved and absorbed by the 
standard calcium hydrate solution in the small flasks. In 
a quarter of an hour or so these flasks are detached, the 
water bath removed from the large flask, and the excess of 
calcium hydrate remaining in the flasks determined by 
titration with deci-normal oxalic acid solution (using aurine 
as an indicator). The small flasks are then cleaned out 
and recharged with the known volume of calcium hydrate 
solution as before, and the large flask containing the water 
heated by the bare flame of an ordinary bunsen lamp, and 
the contents boiled until the steam — passing into the first 
small flask' — heated the same to nearly boiling point; at 
this stage the small flasks are disconnected, and the lamp 
removed from the large flask, the titration of the calcium 
hydrate in the flasks being repeated, and the amount of 
carbon dioxide thus evolved by the decomposition of the 
organic matter determined. Dilute sulphuric acid (about 
20 c.c.) is now poured into the funnel tube and so into the 
large flask, the small flasks recharged with calcium hydrate 
and connected to the large flask as before, and the latter 
again boiled with the bare flame of the lamp as in the last 
determination. The carbon dioxide obtained in this stage 
is mostly that derived from carbonates of calcium and mag- 
nesium in the water. I now take 5 grms. of crystallized 
chromic acid, or an equivalent amount of potassium bichro- 
mate, and dissolve it in 20 c.c. of strong sulphuric acid, and 
pour this mixture through the funnel tube into the flask, 
and repeat the operations as before. The carbon dioxide 
evolved in this stage is derived entirely from organic 
carbon present in the water. 
I have tested this method with the Trwell water aed 
obtained as much as 2’7 grains per gallon of carbon in 
the last stage, and 0’4118 grains of carbon altogether in 
