After having previously roasted the tube and copper oxide, and reduced the copper spiral a, the weighed calcium chloride tube and potash bulbs are put in position, the boat containing the substance is inserted (in the case of a difficultly combustible substance it is desirable to mix it with cupric oxide or lead chromate), the copper spiral (d) replaced, and the air and oxygen supply connected up. The apparatus is then tested for leaks.
The difficultly of the clay litter controversy lies in the lack of objective evidence.
Difficultly volatile liquids may be weighed directly into the boat; volatile liquids are weighed in thin hermetically sealed bulbs, the necks of which are broken just before they are placed in the combustion tube.
They are quite insoluble in water and in salt solutions, and difficultly soluble in dilute acids and alkalies.
Many salts of the acid are known and, with the exception of those of the alkali metals, they are difficultly soluble in water.