222 INTRODUCTION TO GENERAL SCIENCE 



Materials : Calcium hydrate, hydrochloric acid, 5 per cent, 

 blue and red litmus, samples of soil where clover has been 

 growing. 



a. Take some of the soil in a battery jar, and add just enough 

 water to cover it. Stir for a few minutes, and then test the 

 water with blue litmus paper. If the paper turns red, it in- 

 dicates an acid soil. Add a little lime water, or some slaked 

 lime, to the mixture of soil and water, stirring as before. Test 

 again with blue litmus paper. If the soil is still acid, continue 

 to add lime until the soil is neutral. 



6. If the water in the soil in (a) does not indicate an acid, 

 it may be because the acid is too dilute. To concentrate the 

 suspected acid, pour the water from the soil into beaker, and 

 boil down to one twentieth of its original volume. Then test 

 with litmus. 



c. Test dilute hydrochloric acid with litmus, and then 

 neutralize the acid with lime, as in Experiment 65. 



159. COMMERCIAL FERTILIZERS 



The fertilizers which are on the market are usually the 

 so-called complete fertilizers: that is, they contain the phos- 

 phorus, potash, and nitrogen in the proportions which have 

 been found best for general crops. Thus they are not, per- 

 haps, adapted to the particular crops which the farmer wishes 

 to raise, nor do they always supply the plant food which is 

 lacking from a particular field. It is impossible, then, for a 

 farmer to buy a commercial fertilizer which can be very well 

 adapted to his special needs. 



The losses which accrue from the use of commercial fer- 

 tilizers are not confined to this inadaptability to the farmer's 

 needs, but also include the transportation expenses, and the 



