128 



AGRICULTURAL CHEMISTRY 



KOH, commonly called caustic potash, is a white, brittle 

 substance which readily absorbs moisture and carbon 

 dioxid from the air. 



Experiment 26. Preparation of KOH. Dissolve 5 grams potas- 

 sium carbonate, K 2 CO 3 , in an evaporating dish containing 15 cc. of 

 water. Add a mixture of 3 grams Ba(OH) 2 

 and 10 cc. of water. Heat on the sand-bath 

 for five minutes. Filter off the solution. Ob- 

 serve the precipitate. Evaporate some of the 

 solution to dryness in the evaporator. 



Questions. ( i ) Write the reaction which takes 

 place between K 2 CO 3 and Ba(OH) 2 . (2) What 

 is the insoluble white material left on the filter- 

 paper? (3) Is the KOH soluble or insoluble? 

 (4) What other material could be used in place 

 of Ba(OH) 2 ? (5) If NaaCOg were used instead 



Fig. 54. Preparation of K 2 CO 3 , what product would be formed ? Write 

 of KOH. the react i on (5) What reaction does K 2 CO 3 



give with litmus paper? (7) What reaction does NaOH give? 



(8) What are some of the uses made of KOH? (9) What would 



result if the KOH in the evaporator were left exposed to the air 



for a day or so ? 



154. Potassium Nitrate. This salt is found in small 

 amounts in fertile soils where conditions have been favor- 

 able for nitrification processes (see Section 92). It is 

 extensively used in the arts, and is prepared from 

 sodium nitrate deposits which occur as natural products 

 known as Chile saltpeter. It is an oxidizing agent and 

 is one of the ingredients of gunpowder which is a mix- 

 ture of sulfur, carbon and potassium nitrate. Potas- 

 sium nitrate, in small amounts, is occasionally used for 

 the preservation of meats. 



