weighed Erlenmeyer flasks or weighing bottles. A fifteen-gram sample

VOL. 5. No. 2

MOVING AMALGAM ELECTRODES I N CLASS WORK

201

weighed Erlenmeyer flasks or weighing bottles. A fifteen-gram sample is sufficient for most of the amalgam compositions. Weighings are made t o the nearest centigram. The electrode is then replaced in the vessel and the e. m. f. is taken again. The reading should be the same as before t o 0.1 millivolt. The samples are titrated with 0.1 N HC1, with methyl red as indicator. The most effective method of decomposing the amalgam completely is to "swish" i t a t a rapid rate, avoiding any large momentary

E. M.

TABLE I SODIUM AMALGAM

P. COMPOSITION DATA FOR B. I". 1. in 1 M .

Weight per cent N e in amalgam

~LECTRODES

NaCl against

calomel

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Allmand and Polack Allmand and Palack Allmand and Polack Allmand and Po!ack Richards and Richards and Richards and Richards and Richards and

0

Connnt

Conant Conant Conant Conant

Michalek and Phipps I Michalek and Phipps Michalek and Phipps Michalek and Phipps I Michalek and Phipps j

I

0

excess of acid. The addition of platinum scrap did not hasten the decomposition. It is apparent a t once that the data of Table I may be used as the basis of an extremely accurate e. m. f. method of analysis of sodium amalgams, and the experiment can be varied, a t the discretion of the instructor, to emphasize the possibility of such an analytical procedure. The experiment as outlined above has been performed by an electrochemistry class for the past two years, and in nearly all cases the individual values for the potential of the sodium electrode have fallen within a few tenths of a millivolt of the correct value.

Pneumatic Tubes Transport German Steel Samples. Red-hot samples of steel through pneumatic tubes recently installed between a steel mill and its testing laboratory. This novel method of conveyance was installed in order to allow the laboratory to be located away from the smoke and dirt of the mill itself.-Science Sem'ce are shot