On Aluminium Weights.
By DR. T. L. PHIPSON, F.C.S.
For the last ten years—that is, since May, 1860—I have made use of a set of aluminium (division of the gramme) weights. On the average these weights have been used at least twice or three times a day for a period of somewhat more than ten years. They were supplied by MM. Collet, Frères, of Paris. Latterly, I have tested them and found them as accurate as the day on which they were first used. They are almost as brilliant as when new. The larger weights 0.5, 0.2, and 0.1 gramme show slight traces of tarnish, but their weights are still quite accurate.
During this period of ten years these weights have never been touched except by a pair of soft brass nippers, and they have never been left exposed to the air for more than a few minutes at a time. However, they have, of course, been exposed for a minute or two at intervals to an atmosphere more or less impregnated with acid or alkaline vapors, and if we add these odd minutes together, it will be found that these gramme divisions in aluminium have had to undergo a considerable amount of "atmospheric influence" during the period of which I speak.
I need scarcely say what a luxury it is to use such large weights as these in comparison to the platinum gramme divisions, and I am surprised that they are not more generally adopted in our laboratories. The set contains 14 weights, from ½ a gramme to ½ a milligramme.
As to brass or copper divisions, I have always considered them inaccurate, for they tarnish very rapidly in an atmosphere which, for that of a laboratory; might be considered tolerably pure. Weights of maillechort (a kind of German silver) resist much better than copper or brass weights; I have a set since the year 1856, the gramme divisions of which extend only to the centigramme, and are perfectly bright and accurate at the present day, but they have only been used occasionally.
The Cedars, Putney, S. W., October 10th, 1870.
—Chem. News, London, Oct. 14, 1870.