§ V. Gaseous Contents of the Water.
A quantity of the water measuring ten cubic inches, being boiled briskly over mercury, the gas given out, together with the air contained in the apparatus, was received in a graduated tube; on admitting caustic alkali into the tube, one-tenth of a cubic inch of gas was absorbed. It appears therefore that one hundred cubic inches of the water contain one cubic inch of carbonic acid gas, which is equivalent to about three-tenth of a cubic inch to each pint. The water was uncorked at the moment of being examined, but I had not an opportunity oft ascertaining the quantity of gas.
§ VI. Evaporation of the Water, and Estimation of the Quantity of solid Ingredients.
1. Sixteen ounces of the water by measure, being evaporated down to a soft mass over a lamp, and afterwards desiccated in a drying apparatus at the heat of 180°,[1] the solid mass weighed eighty-six grains. During the evaporation the same appearances were observed as have been already related (in § III., D,) and the dry saline mass assumed a pale greenish colour. On standing in the air, it slightly deliquesced, and its colour became somewhat darker. This saline mass, though slowly evaporated, never assumed a distinct crystalline appearance.
- ↑ This is the heat I have usually employed for desiccation, because it is that which is obtained by the water-bath which I use, and can scarcely be raised higher by that apparatus. By a heat of 180° however, I generally mean some intermediate point between 170° and 180° for it is impossible to regulate the temperature with perfect accuracy.
