126 CHEMISTRY FOR AGRICULTURAL STUDENTS 



124. What is the action of ferrous sulphate upon nitric acid? Describe 



how it may be used as a test for nitrates. 



125. What is the action of nitric acid on indigo solution? Describe how 



it may be used as a test for nitrates. 



1 26. What do you know about the solubility of metallic nitrates ? 



•^127. Distinguish the nitrite from the nitrate. (Sodium nitrite and sodium 



nitrate.) 

 *I28. Volumetrically determine the strength of the nitric acid. 

 *I29. Identify the gaseous oxide of nitrogen. (Nitrous oxide, nitric oxide, 



and nitrogen peroxide.) 

 *I30. Prepare a bottle full of nitrogen gas 



Putrefaction and Nitrification. 



131. What is meant by the terms putrefaction and nitrification? 



Account for the nitrate of potassium found as an efflorescence on 

 the soil round an Indian village, the nitrate of calcium crystals on 

 a stable wall, and the deposits of nitrate of sodium in Chili. 



132. What is the danger in the use of water contaminated with sewage 



for drinking purposes ? An analyst's report upon a water is given 

 in terms of "oxygen absorbed," "albuminoid ammonia," 

 "free ammonia," "nitrates," and "chlorine." Discuss the 

 importance of each. 



133. State the conditions that are necessary to promote putrefaction and 



nitrification. How would you apply these conditions (i) to the 

 purification of drinking water, and (2) to the increase in fertility 

 of the soil ? 



134. Of the nitrates or ammonium salts of the soil, which are found 



most abundantly in drainage waters from arable land ? Under 

 what conditions does loss of nitrate from the soil occur most 

 freely, and how may it be prevented? Discuss the use of 

 sulphate of ammonia instead of nitrate of soda as a manure. 



135. Report upon the suitability of the water for drinking purposes. Is 



it almost free from organic matter, nitrates, and chlorides ? 



Phosphorus and Phosphoric Acid. 



136. What compound does phosphorus form with hydrogen? Mention 



two cases in which its production may be observed. 



137. Is phosphorus easily oxidised? Does it oxidise at the ordinary 



temperature ? What is meant by "phosphorescence " ? 



