PRACTICE XII 



PREPARATION OF POT CULTURES 



Use clean, white, sifted quartz sand in 5-liter heavy glass battery 

 jars, having a 1-cm. hole within 1 cm. of the bottom. Into the hole 

 fit a drain tube made of glass tubing with a glass-wool filter at the 

 inner end, so that it will drain from the lowest part of the jar. Put 

 up a series of eight of these pots, to be used as indicated in the 

 table on the following page. 



To extract the sand, fill the jar within 1 cm. of the top with dry 

 sifted sand and add to this dilute sulfuric acid (made by adding 

 100 cc. of concentrated chemically pure sulfuric acid to 900 cc. of 

 ammonia-free water) until the sand is saturated. Let stand two 

 hours and then add ammonia-free water, allowing the drainage to 

 flow into a second jar until it is saturated. Allow this jar to stand 

 two hours and then wash both with ammonia-free water until free 

 from acid. 



After drying, mix with the sand of each pot 10 g. of pure calcium 

 carbonate. 



In making applications of plant food as indicated in the following 

 table, and in such amounts as are shown in Practice XI, bring the 

 solutions to be applied to each pot into about 1 liter of water, mix 

 thoroughly, and apply the whole amount to the pot, allowing any 

 water present to be forced out through the drain. 



The first application of plant food is to be made at the time of 

 planting, the second three weeks later, the third two weeks later, 

 and subsequent applications at intervals of one week, each time 

 making the application as directed above. 



Each student in each group will prepare and care for a series 

 of pots, as indicated in the following table. 



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