PROOFS OF THE PROPERTIES OF COPPER.

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Tomlac is obtained in a like manner by fusing together in acrucible twelve parts of copper and three of zinc.

Gun-metal is said to consist of copper alloyed with one tenthpart of tin.

Bell-metal is copper alloyed with about one-sixth of tin; itmay in general be observed that a less proportion of tin is usedfor making church-bells than clock-bells, and that a little zincis added for the bells of repeating watches, and other small bells.

The metal of which cocks are in general made is copper al-loyed with zinc and lead.

Experiment VI.

Concentrated, sulphuric acid only acts upon copper at elevatedtemperatures.

Pour upon one ounce of oopper filings in a matrass, twoounces of concentrated sulphuric acid, there will be no action inthe cold; but if the matrass be placed on a sand-bath, and a de-gree of heat applied nearly sufficient to make the acid boil, the.copper will be gradually dissolved and sulphureous acid gas willbe liberated.

Experiment VII.

Copper unites with arsenic acid, and forms a compound, calledScheele's green.

This colour is formed by decomposing sulphate of copper bythe arseniate of potash, in the following manner:

Dissolve potash in water with heat; add white oxid of arsenicor arsenic acid to the point of saturation, and filter the liquor.