VARIATION OF DUDLEY AND NOYES 



dried ammonium oxalate in solution, with a little dilute sulfuric 

 acid and with ammonium ferrous sulfate partly crystallized in 

 small crystals from a slightly acid solution. The crystals should 

 be well washed and quickly air-dried in a thin layer. The factors 

 - and - should be used, respectively, to calculate the iron equiv- 

 alent. The phosphorus equivalent is obtained by multiplying 

 the iron equivalent by _li_ =0.0 1538. 



Reduction Apparatus. The reduction of the molybdic acid to 

 molybdenum trioxid is accomplished in a tube first proposed by 

 Jones. The apparatus is shown in Figure 8. A piece of moder- 



Fig. 8. Jones' Reduction Tube. 



ately heavy glass tubing 35 centimeters long, with an internal 

 diameter of two centimeters, is drawn out at the lower end so as 

 to pass into the stopper of a flask. A circular piece of perforated 

 platinum or porcelain rests on the constricted portion of the tube 

 and this is covered with an asbestos felt. The tube is then nearly 

 filled with powdered zinc, which is washed, before using, with 



