36 MILK 



water, the rinsings being collected in the beaker. 

 The liquid is heated untU all the copper is in 

 solution, filtered, the filter washed until the 

 filtrate amounts to at least 100 c.c, and elec- 

 trolyzed. 



Electrolytic apparatus has been constructed 

 in a great variety of forms. When the opera- 

 tion is carried out frequently, it is best to have 

 an electrolytic table. A platinum basin holding 

 not less than 100 c.c. is used. A cylindrical form 

 with flat bottom is convenient. It should rest 

 on a bright copper plate, which is connected 

 with the negative pole of the electrical supply. 

 The positive pole should be also platinum, either 

 a spiral wire, cylinder, or flat foil. Many 

 operators use a funnel-shaped perforated ter- 

 minal for the negative pole ; in which case a glass 

 beaker or casserole wiU be a suitable container, 

 the positive terminal being placed within the 

 negative. 



Pour cells of a gravity battery will suffice 

 for a single decomposition, and will operate 

 two, but more slowly. It is usual to arrange 

 the apparatus so that the operation may be 

 continued during the night. When the elec- 

 tricity is taken from the general supply of the 

 laboratory, it is usually necessary to interpose 

 resistance and to have some means of measuring 

 the current-flow. This is sometimes done with 



