Warren C. WoeWel
University of Arizona Tucson, 85721
A System for Packaging and
Numbering Solid Unknowns
Solid unknowns can he packaged conveniently in household aluminum foil. We have found that pieces 2l/, in. X 4'/% in. are a good size (see figure). The foil can be made into a trough by forming the sides over a a/,in. piece of wood. An appropriate amount of solid is placed near one end, the sides are folded over and the rectangle thus formed is folded V 8 in. from the end, then twice at one inch intervals, leaving a tab about 1 in. long. The code number can be written on this tab (the dull side of the foil is better.) The table suggests blocks of consecut,ive numbers as a code for each cation and anion. The Dmxing representing tho initial of the bloclcs is folding of the sample package (left1 ond the Rnd, numbered chosen as demanded by packet
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/ Journal of Chemical Education
the total number of samples, admissibility of repetitions, etc. The table shown allows for 40 packets of each salt. For example, CaBr2 would he identified by 40 diierent numbers: 21.9 to 25.16. The code also allows for the variation of numbering the anion first, e.g. 65.16 for MgCO,. A warning to be observed is that mercury(I1) salts react vigorously with aluminum foil in the presence of moisture. Example of a Code Numbering System for Solid Unknowns Cations
Anions
