III (Ley Pewter).—From tin, 80 per cent; lead, 20 per cent. Used for measures, inkstands, etc.
According to the report of a French commission, pewter containing more than 18 parts of lead to 82 parts of tin is unsafe for measures for wine and similar liquors, and, indeed, for any other utensils exposed to contact with food or beverages. The legal specific gravity of pewter in France is 7.764; if it be greater, it contains an excess of lead, and is liable to prove poisonous. The proportions of these metals may be approximately determined from the specific gravity; but correctly only by an assay for the purpose.
Silver Alloys:
Aluminum Silver.
The properties of aluminum and silver alloys vary considerably according to the percentage of aluminum.
I.—An alloy of 100 parts of aluminum and 5 parts of silver is very similar to pure aluminum, but is harder and takes a finer polish.
II.—One hundred and sixty-nine parts of aluminum and 5 of silver make an elastic alloy, recommended for watch springs and dessert knives.
III.—An alloy of equal parts of silver and aluminum is as hard as bronze.
IV.—Five parts of aluminum and 1 part of silver make an alloy that is easily worked.
V.—Also aluminum, 3 parts, and silver, 1 part.