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The conditions necessary for making thick electrodeposits of zinc on zinc starting sheets were investigated with the object of eliminating the stripping costs and reducing melting losses, which occur under the present practice of using aluminum starting sheets. Finished cathodes as thick as 2.6 inches (6.6 cm) were produced on sheets rolled from four‐nines zinc, and cathodes as thick as 1 inch (2.5 cm) were produced on sheets of commercial grade zinc. These results were obtained by rigorous purification of cell feed solution and by using cathodes of special design. Compared to present aluminum starting sheet costs, the use of zinc starting sheets is expected to offset in part, if not completely, the expense of the extra liquor purification step. This would leave intact the savings effected by eliminating the zinc stripping step and by reducing melting losses.

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Zinc sheet from three different sources and aluminum sheet have been compared to determine their relative reliability as starting-sheet material for the electrodeposition of zinc from acid solutions. The aluminum sheet was used with edge strips, as required by present commercial practice, and without edge strips. The materials were tested in electrolytes with a wide range of impurity eonten~. Average residence period was used as the measure of reliability.

A trap has been devised which prevents the escape of certain gases into the laboratory. The gases are forced to escape into a neutralizing gaseous atmosphere. The trap is successful in a room without hoods or unusual ventilating facilities. The principle involved is general and has wide application.Among the problems confronting the teacher of laboratory courses in chemistry the prevention of the escape of offensive gases into the room is perhaps less amenable to treatment than others. Student carelessness of course leads in the list of reasons why such gases should escape but the experienced teacher will agree that this is a fault which is always generator present and difficult to correct. Any scheme of prevention must take this into account if any