161, 162] Analysis of Grass and Hay 107 



placing a disc of glass just inside the beaker, and squeezing as 

 shown in fig. 42. 



After this treatment all matter which is soluble in water 

 will have been removed. It remains now to extract the 

 colouring matter. This often takes ^ 

 some time. It is done by soaking in 

 alcohol for an hour at a time, straining 

 off the spirit after each soaking until 

 it runs off colourless. Ether is then 

 used until the fibre is quite white. It 

 is then dried and weighed in the same 

 manner as the woody fibre. 



Considerable annoyance is frequently caused in this opera- 

 tion by the evaporation of the ether, especially when the fibre 

 is allowed to soak over night. This may, to a very great 

 extent, be prevented by placing over the mouth of the beaker 

 half-a-dozen thicknesses of filter paper, covering these with 

 a glass disc, and placing a small weight on the top of the disc. 

 In this way the beaker is made fairly air-tight, and much less 

 loss occurs than when the beaker is merely covered with a 

 clock glass. 



The crude fibre must be ground up, bottled, and labelled. 



So far the only constituents which have been estimated are 

 moisture, woody fibre, and crude fibre. The two bottled por- 

 tions may now be proceeded with. 



Analysis of the ' Dry Matter ' 



161. Before any portion is weighed out, the 'dry matter' 

 must be heated in the steam oven for an hour and cooled in 

 the desiccator. This is necessary, as the powdered substance 

 is very hygroscopic. 



162. Total Nitrogen. — Weigh out about 2 grams of the 



