Silver iodide, mercurous iodide, and mercuric iodide are insoluble in water; lead iodide is sparingly soluble, whilst most of the other metallic iodides are soluble.
Aurous oxide, Au 2 0, is obtained by cautiously adding potash to a solution of aurous bromide, or by boiling mixed solutions of auric chloride and mercurous nitrate.
Many are readily soluble in water, the chief exceptions being silver chloride, mercurous chloride, cuprous chloride and palladious chloride which are insoluble in water, and thallous chloride and lead chloride which are only slightly soluble in cold water, but are readily soluble in hot water.
After the platinum wires have been sealed through the glass, a little aqua regia is placed in the cell legs until bubbles of gas arise from the platinum, when it is thrown out and replaced by a solution of mercurous nitrate.
In this meter the electrolyte is a solution of mercurous nitrate which is completely enclosed in a glass tube of a particular form, having a mercury anode and a platinum or carbon cathode.
The mercurous sulphate must be free from acid, and made neutral by trituration with finely divided mercury.
In its properties it shows some analogy to the halogen acids, since it forms difficultly soluble lead, silver and mercurous salts.
The sesquioxide, Cr 2 0 3, occurs native, and can be artificially obtained in several different ways, e.g., by igniting the corresponding hydroxide, or chromium trioxide, or ammonium bichromate, or by passing the vapours of chromium oxychloride through a red-hot tube, or by ignition of mercurous chromate.
A sublimate may be formed of: sulphur - reddish-brown drops, cooling to a yellow to brown solid, from sulphides or mixtures; iodine - violet vapour, black sublimate, from iodides, iodic acid, or mixtures; mercury and its compounds - metallic mercury forms minute globules, mercuric sulphide is black and becomes red on rubbing, mercuric chloride fuses before subliming, mercurous chloride does not fuse, mercuric iodide gives a yellow sublimate; arsenic and its compounds - metallic arsenic gives a grey mirror, arsenious oxide forms white shining crystals, arsenic sulphides give reddish-yellow sublimates which turn yellow on cooling; antimony oxide fuses and gives a yellow acicular sublimate; lead chloride forms a white sublimate after long and intense heating.
In the case of the Clark standard cell above mentioned the elements are mercury and zinc separated by a paste of mercurous sulphate mixed with a saturated solution of zinc sulphate.