A Rapid Visual Test for the Quantitative Determination of Small Concentrations of Calcium in Lead

manufacture of lead-calcium is INtheTHEcombination oftoproperties..005Sincesheathinitorderdesirable tothecontrol calcium content 0.028 ± per cent to obtain most desirable calcium is a very active element chemically, special manufacturing procedures were developed to minimize the contact of molten lead-calcium alloy with the air. Despite the improved techniques, some calcium is always lost and must be replaced. Before this can be accomplished satisfactorily, obviously, the calcium content of the alloy must be determined. Conventional chemical procedures are accurate but not entirely satisfactory for plant control use because they are time consuming and too costly. The best of the chemical methods introduces a lag of at least two hours in melting kettle control. Quantitative spectrographic analysis methods were carefully tested, and while they showed some advantage over conventional methods, they were still unduly time consuming. With the ever increasing interest in lead-calcium alloys for cable sheath, storage-battery grids, and other applications, it became desirable that a rapid, reliable and not too costly method be developed for determining their calcium content. In approaching the problem, several methods of attack involving physical, chemical, or electrical properties suggested themselves. A few of the methods investigated were: 1. Observations of the rate of oxidation or tarnish of freshly cut surfaces using a variety of atmospheres and temperatures. 2. Thermal E M F measurements against pure lead.