H4 CHEMICAL FERTILIZERS 



the cod. In Brittany a similar article is produced by boiling 

 the fish debris and pressing between iron plates, whereby 

 an article containing about 6-7 % of nitrogen and 29-39 % 

 of phosphates is obtained. Norwegian fish guano is chiefly 

 obtained from cod, and is produced in a similar way 

 to that of the British meal ; it generally contains about 

 7-8 % of nitrogen and 12-15 % of phosphates. In the 

 U.S.A. 9 % of nitrogen, 15 % of phosphates and 7 % of oil 

 is the usual composition of fish guano obtained by a boiling 

 and pressing process. 



Blood Manures. Fresh blood forms a red, thick liquid, 

 which, in contact with air, soon separates into two parts 

 the solid fibrous part, which forms a clot, and the liquid 

 part, which constitutes a serum. Of the total blood about 

 20 parts is solid matter, the remainder being water. The 

 percentage of nitrogen in fresh blood is about 3 %, while 

 the amounts of phosphoric acid and potash are almost 

 negligible. Blood is generally dried by steam in an open 

 pan, after the addition of a quantity of ferric sulphate 

 solution, equal to about i part of solid, dry ferric sulphate 

 per 100 parts of blood. The object in using ferric sul- 

 phate is to coagulate the colloids in the blood, which 

 make it difficult, and even dangerous, to boil. All colloids 

 froth readily, as may be noticed when boiling milk. The 

 coagulated blood is usually allowed to drain, whereby a 

 certain amount of liquid runs away. More expeditious and 

 less offensive methods have been devised which use a rotary 

 steam-heated drier, connected to a vacuum receiver. Blood 

 which has been coagulated and dried very carefully and 

 slowly below 100 C. may contain as much as 13-14 % 

 of nitrogen, but the ordinary kinds of black blood manure 

 contain usually only between 6 % and 10 %. Blood can also 

 be dried very readily by lime. One hundred parts of blood 

 are mixed with from i to 3 parts of quicklime, which converts 

 the blood into a solid cake that can be dried in the air 

 without any putrefaction. The resultant mixture falls 

 down to a fine, inodorous powder. No special plant is 

 required for this method, which possesses the additional 



