46 PRACTICAL AGRICULTURAL CHEMISTRY [123-126 



Keep the test-tube containing the platinum foil and liquid 

 for the next experiment. 



* 123. Phosphates in Grass.— To the water in the 

 test-tube (paragraph 122) add an equal volume of dilute 

 nitric acid and warm. Decant the liquid into another clean 

 test-tube, leaving the platinum foil behind. To the clear 

 liquid so obtained add an excess of ammonium molybdate 

 solution and boil ; a yellow precipitate will appear, showing 

 that the grass contained phosphates. 



Roots 



124. Turnips.— Roots, such as turnips, swedes, and 

 mangels, differ from the foods which have been considered, 

 in that they contain a very much larger proportion of water 

 and a greater quantity of sugar. When the water is squeezed 

 out of the roots it brings the sugar and other soluble sub- 

 stances with it. Hence the components of a turnip may be 

 divided into two kinds : the soluble, which with the water 

 constitute juice, and the insoluble, which go by the name of 

 crude fibre. The crude fibre is very much like hay in its 

 constitution ; therefore the experiments here described are 

 intended only to show the properties of the juice. 



125. Juice in Turnips.— Cut a turnip up into six 

 sections with a large knife. Grate up one or two of these 

 sections on a bread-grater, allowing the pulp to fall on to a 

 piece of linen stretched over a porcelain tile. When a good 

 handful of pulp has been thus prepared, fold it up in the 

 cloth and squeeze out the juice into a beaker. Throw away 

 the fibre left in the cloth and with the juice perform the 

 experiments described in paragraphs 126 and 129. 



126. Sugar in Turnips. — Taste a little of the juice. 

 It has the flavour of raw turnip, but is nevertheless very 

 sweet. Pour sufficient juice into a clean test-tube to fill 

 about half an inch of the tube. Dilute this with about four 

 times its volume of water, then add about an equal volume 



