PROOFS OF THE PROPERTIES OF TIN*

97

SECT. II.

EXPERIMENTAL PROOFS

OF

THE PROPERTIES OF TIN

Experiment I.

Tin unites to oxigen in different proportions.

JLjET this metal be melted in an iron ladle in contact with air;its surface will become covered with a grey pellicle, which formswrinkles; when this is taken off, it is soon succeeded by another,and in this manner the whole metal may be converted into apowder, which is yellow or grey oxid of tin. To free it fromthe particles of tin which are not oxidated, it must be passedthrough a sieve of lawn or silk. It is extremely difficult toseparate it entirely from the tin, it therefore is of a grey colour.

Let the oxid of tin, obtained in the above process, be exposedto a red-heat in a crucible, or an earthen capsule under a mufflefor some time, stirring it occasionally with an iron rod, and itwill become more oxidated, and acquire a white colour. Thisis white oxid of tin, commonly called putty of tin. It is used forpolishing glass specula for telescopes, marble, steel, See. It de-prives every kind of glass of its transparency,^ and converts itinto white enamel.

Vol. II.

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