CH. V.] 



METHOD OF AMOS PETERS. 



137 



heated gauze. By means of a stop-watch note the time for the 

 temperature to rise from 35 to 95. If the time is greater or less 

 than 120 sees, loosen or tighten the screw A and repeat the experi- 

 ment with another 60 cc. of distilled water until the temperature of 

 the water rises from 35 to 95 in 120 2 sees. The height of the 

 ring and the thickness of the asbestos should be such that the pressure 

 is well under the minimum supplied to the laboratory and yet 

 sufficient to prevent any risk of the flame striking back. Note the 

 manometer reading. The standard heating power can be rapidly 

 obtained for further experiments by adjusting the screw A so that 

 the manometer shews the requisite pressure. 



Filtering Apparatus. It is convenient to use the apparatus 

 shown in Fig. 16. A is a " Duro " flask of 200 cc. capacity. Tube B 



is an ordinary calcium chloride 

 tube. The lower end should 

 reach at least 3 cm. below the 

 lower edge of the stopper to 

 prevent loss by splashing during 

 filtration. The filtering mat is 

 made of glass wool, asbestos 

 fibre, powdered pumice and 

 asbestos fibre added in that 

 order. The mat should be 

 washed with nitric acid and then 

 thoroughly washed with water. 

 After a test the cuprous oxide 

 on the mat is dissolved in nitric 

 acid diluted with an equal 

 volume of water and then 

 thoroughly washed. 



An ordinary Gooch crucible 

 can be used with a mat pre- 

 pared in the same way. The 

 arrangement is shewn in fig. 33, p. 259. 



Fig. 1 6. Filtering apparatus for 

 reduced copper. 



Method of Analysis. Into a 200 cc. Erlenmeyer flask measure 

 20 cc. of the standard copper sulphate, 20 cc. of the alkaline 

 tartrate, and 20 cc. of the sugar solution (which must not contain 



