and Laboratory Methods. 1499 



CADMIUM. 



A. Cadf?ii urn from Magnesiian. 



The bulk of the magnesium can be precipitated as magnesium ammonium 

 phosphate by adding ammonium hydroxide and sodium phosphate, the latter 

 very carefully and only a very little at a time so as to avoid precipitating any 

 cadmium. The clear supernatant solution is then drawn off and tested for 

 cadmium. 



B. Cadmimn from Gluciniitn, Zinc^ or Aluminum. 



Precipitate with excess of sodium or potassium hydroxide. Glucinum, zinc, 

 and aluminum are dissolved. Cadmium remains insoluble. Dissolve the pre- 

 cipitate in hydrochloric acid and test with oxalic acid or with sulphocyanate. 



C. Cadmium in Complex Mixtures. 



Proceed as in the above described methods in which ammonium hydroxide 

 and ammonium carbonate, etc. ; e. g.. Zinc C. After precipitation and ignition 

 of the oxalates, the residue is extracted with sodium hydroxide, cadmium remains 

 insoluble. This residue insoluble in sodium hydroxide is washed, dissolved in 

 hydrochloric acid, and tested for cadmium. 



D. Cadmium frofn Zinc. 



See Zinc B. 



E. M. Chamot. 



Cornell University. 



A Damp Chamber for Use on the Khnostat. 



Students of Plant Physiology have often found need for a damp chamber for 

 use on the klinostat which will furnish a firm support for seedlings in rapid 

 rotation and will retain a supply of moisture for several hours. The original 

 method used by Knight has been variously modified so as to provide moisture 

 for the plants. In cases where the desired plane of rotation is horizontal the 

 experiment may be successfully performed by covering with a bell-jar a rotating 

 disk whose axis projects below the table and to which the motive power is applied. 

 In work where the desired plane of rotation is vertical, some experimenters have 

 arranged a reservoir of water so that the supply of moisture falls upon the rotat- 

 ing seedlings in drops ; but here is a chance that the thigmotropic or traumotropic 

 stimulus given by the falling drops may affect the results of the experiment. 



The apparatus described below has been successfully used for different 

 kinds of work in the Botanical Laboratory of the University of Michigan. 



A narrow board, containing about eight pegs 5 or 6 cm. long, is fitted into the 

 bottom of a thin glass basin of about 22 cm. diameter and G cm. depth. The 

 pegs serve for the attachment of the small bars holding the seedlings. The glass 

 dish is lined with moist filter paper and closed with a circular glass plate 24 cm. 

 in diameter ; the inner side of the cover is completely lined with a piece of 

 moist blotting paper, which forms an almost perfectly tight fitting cover. 



