VOL. 7, No. 5
T H E CHEMISTRY STUDENT
1153
15. To write chemical equations. (For the hydrolysis of starch to glucose, and the neutralization of the sulfuric acid.) 16. To calculate the required weight of one substance to react with a known weight of another. (Calculated weight of barium hydroxide added to known weight of sulfuric acid.) 17. To choose the proper hydroxide for a special case of neutralization. (Barium hydroxide chosen because it leaves only an insoluble sulfate and water.) 18. To make use of solubility rules and tables. (Solubility of barium hydroxide in hot water, and insolubility of barium sulfate.) 19. To use precipitation as a means of separation. (Sulfuric acid removed as precipitated barium sulfate.) 20. To increase the concentration of a solution. (Evaporation of thin liquor to thick sirup.) 21. To use evaporation as a means of concentration. (Getting the sirup from the liquor.) 22. To use charcoal to adsorb undesirable colors, odors, and tastes. (Purification of sirup by use of animal charcoal.) Beside the chemical and scientific educational value of such a project, it has very distinct values in other fields of education as well. The head of our English department tells me that the ante-project reading and notetaking and the post-project writing and speaking before the class embody almost if not quite as many English objectives as the actual work employs in the field of chemistry. I t would seem theqthat the great educational possibilities of such a project removes it far from the classification of a "chemical stunt," and place it on a firm foundation of practical education. Melting Point of Palladium. The highest standard point in the thermometric scale which can be measured conveniently with the gas thermometer is the melting point of gold, 1063°C. Above this, recourse is ususlly made to radiation thermometry, with, for technical purposes, an agreed value for the radiation constant (0).I t is, however, useful t o have other higher fixed points, and of these the most important is the melting point of palladium. One determination of this was reported in the Bureau of Standards Journal of Research for May of this year, yielding the value 1554'. A second determination, made a t the National Physical Laboratory by F. H. Schofield, is described in the Proceedings of the Royal Society for October, and gives the temperature as 1555". Older determinations, made a t the Physikalisch-Techni& Reichsanstalt in 1919 (15567, and a t the Nela Laboratories in 1920 (1557O), are also in remarkably good agreement with the new numbers, and i t thus seems probable that the agreed value of 1555O which has been taken as the melting point for the purposes of the International Temperature Scale cannot he in error by more than 2'. It is an interesting fact that Prof. Callendar obtained a value only five degrees below this in 1899, working with a resistance thermometer of platinum, and extrapolating from the boiling-point of sulfur.-Nature
