WASTE PRODUCTS 123 



The above tests may be carried out on a mixed 

 fabric, if obtainable. By soaking in cold strong HCl 

 for some time the silk is removed. After washing, the 

 remainder is boiled with 10 per cent. NaOH, which 

 dissolves out the woollen fibres. The remainder is 

 cotton or linen. 



106. A nalysis of Fibrous Waste Products. 



{a) Sampling. — As large a parcel as possible should 

 be well mixed, spread out, and fairly sampled for 

 analysis. Coarse portions of fabric, etc., must be cut 

 into small pieces and distributed throughout the mass. 



{U) Moisture. — Measured by drying at 100° C. 



{c) Sandy Material. — Obtained, together with the ash, 

 by incinerating a few grams of material and strongly 

 igniting until the residue is free from carbonaceous 

 matter. 



id) Oil — About 10 grams of the material are 

 thoroughly extracted with light petroleum in a Soxhlet 

 apparatus into a weighed flask. The solvent is 

 removed and the residue dried and weighed (see 12, 

 p. 19). 



{e) Nitrogen. — Estimated by the Kjeldahl process, 

 using the factor 6-25. 



107. Examination of other Nitrogenous Waste Products. 



(a) Sampling. — The difficulty of examining products 

 like skin and fur wastes, rabbit flick, slaughter-house 

 refuse, etc., generally consists in the sampling. Very 

 large pieces must be removed and the proportion 

 measured, since they will have little manurial value. 

 Smaller pieces must be cut up and incorporated with 

 the main bulk previous to sampling. 



Leather dust, horn and hoof dust or shavings, 

 dried blood, etc., are generally easy to sample. 



