MANUAL OF GENERAL AGRICULTURE. 07 



some carbon would be consiimed as carbon dioxid. Fin- 

 ish evaporating in a water bath, then heat in an oven at 

 100 C. or 212 F. for fifteen minutes. Cool and weigh. 

 Place again in the oven for fifteen minutes. Cool and 

 weigh, and if the two weights are the same, get per cent by 

 dividing the weight of the milk after water is evaporated 

 out by the weight of the milk taken. The result will be 

 the per cent of total solids in the milk. What is the per 

 cent of water? Transfer to a clean crucible and place 

 over a flame and burn off the organic material. Burn 

 until the ash is perfectly white. Cool and weigh. Divide 

 the weight of the ash by the weight of milk taken and the 

 result is the per cent of ash in the milk. This ash con- 

 tains the mineral salts. Save for the next experiment. 



72. TESTS FOR THE MINERAL SALTS IN THE ASH 

 OF MILK. 



Sodium and Potassium. Treat 1-3 the ash of milk ob- 

 tained in the previous experiment with 10 c.c. distilled 

 water. Filter and test 1-3 the filtrate with litmus to see 

 if it is neutral. Dip a platinum wire in this 1-3 and test 

 for potassium and sodium in the flame. Use purple glass 

 for potassium as in the presence of sodium, potassium can- 

 not be seen. 



Chlorids. Test the second portion of the distilled 

 water solution for chlorids by acidifying with a few drops 

 of nitric acid, and adding one drop of silver nitrate solu- 

 tion. A white cloudiness shows chlorids. 



Iron. To the remainder of the distilled water solution 

 add a few drops of hydrochloric acid. Add a few drops 

 of potassium ferrocyanid. Let stand a few minutes. A 

 blue color shows iron. 



Calcium and Magnesium. Take the second portion of 

 ash and add 10 c.c. warm hydrochloric acid. Note if any 

 gas is given off. If so carbonates are present. To the 

 hydrochloric acid solution, add ammonium hydroxid un- 

 til alkalin. (Test with litmus.) Add an equal amount 

 of ammonium oxalate and heat to boiling. A white pre- 

 cipitate shows the presence of calcium. Filter this and 



