62 CHEMICAL MANUEES. 



after disintegration by the pick and breaking up on the spot — to 

 screen them by throwing them on a trelhs of iron wire called a 

 billard, the square meshes of which are 8 to 20 mm., or a screen 

 of iron bars 8 to 10 mm., say one-third to two-fifths inch apart, so as 

 to free them from one-third or sometimes one-half of their impurities, 

 but at the same time small nodules and fragments broken off by 

 shock are lost. This method is profitable when the nodules are not 

 friable, and easily separated from their gangue. Screening is followed 

 by washing with a current of water in mechanical washers, or in 

 washers fitted with blades, or dry sorting known as fanage. The 

 phosphate nodules occur near the outcrop of the Greensand at a 

 shallow depth, and the sock of the plough often brings them to the 

 surface. An extensive business is done in collecting them and 

 selling them in bulk to the phosphate cleaners. Fanage consists in 

 passing the raw material through a screen after exposure to the air, 

 so as to dry it completely and thus render the argillaceous sands 

 more easily separated from the nodules. The operation is repeated 

 five or six times so as to get a satisfactory cleaning. Drying is facili- 

 tated by spreading the nodules in a thin layer on the ground and 

 turning them like hay, and from that comes the name given to the 

 process. Fanage only succeeds if the gangue lends itself to the 

 process. The nodules fanes, poorer than washed nodules, contain 

 10 to 15 per cent of impurities. They are exposed to rain to 

 wash the impurities away as mud. Fanage is completed by rapid 

 washing. 



Sorting and Sale of Baw Phosphates. — Eaw phosphates are 

 sold by P2O5 content. Thev are bagged up into 5 grades each 

 differing by 5 units— 50-55, 55-60, 60-65, 65-70, 70-75, 75-80 per 

 cent. It is thus easy to supply any strength required. To control 

 strength of wagon loads, buyer's and seller's agents take counter scaled 

 samples at station from each wagon, four random samples from 25 to 

 30 bags. One is tested by seller's chemist, the other by the buyer's. 

 When there is more than 2 per cent between the results, the third 

 sample is analysed by a third chemist and the average of the nearest 

 taken. The fourth sample is kept as a check. In case of ship- 

 ment the goods are sampled in the wagons as they reach the harbour. 

 Sampling is done either by the broker alone or by the broker in 

 presence of the seller's agent. 



Different Methods of Strengthening and Utilizing Poor Quality 

 Phosphates. — Numerous methods have been suggested to utilize 

 the large quantities of low grade phosphates unfit for making super- 

 phosphates. These methods consist of (1) To fortify them in various 

 ways ; (2) To free them from the sesquioxides of iron and alumina, 

 or (3) To increase their solubility or to extract from them their 

 phosphoric acid. But none of these processes have been adopted 

 in actual practice, because they are too costly and incompatible with 



