68 CHEMICAL MANURES. 



As regards the simplicity of the process, the installation of the 

 first superphosphate factories was very primitive. They contained 

 little or no machinery. Three sheds, one to cover the raw phos- 

 phates, the other the den in which to dissolve the phosphate, and 

 the third the superphosphate. So much for the factory. The tools 

 in the beginning consisted of a few harrows, hoes, rakes, and a 

 sieve called a screen — that was all. As to the indoor installation, 

 it included a sulphuric acid tank, a few lead-lined measuring tanks, 

 and three or four rectangular round or square dens. These dens 

 were first made of brick steeped in l:)oiling tar ; afterwards cast-iron 

 cases one inch thick, and sunk in the ground, were used. The 

 method of manufacture was the following. A certain amount of 

 ■sulphuric acid of 50^ to 5T B. was run into the den ; at the same time 

 the phosphate was weighed and heaped on the edge of the den. Three 

 men, each armed with a rake, agitated the acid, whilst the third 

 gradually shovelled in the phosphate. The mass soon thickened, 

 and even set before the "mixing" was complete. Nevertheless, to 

 obtain a homogeneous mixture the mass was triturated by bringing 

 it from one side of the den to the other ; finally it was filled into 

 barrows and shifted into the superphosphate shed. There it lay in 

 heaps for a month ; finally it was hand screened and sent out to 

 customers. When well dissolved, it gave no core, any lumps 

 being crushed by the back of the shovel, until sufticiently fine to 

 pass through the screen. By such simple means sufficiently dry 

 superphosphates were obtained, comparatively fine and well dis- 

 solved. These methods sufficed then, because the very pure raw 

 phosphates were delivered in the ground state, or at least sufficiently 

 fine to pass through the screen. 



1871 to 188Q. — As raw phosphates, spent bone l^lack from sugar 

 w^orks, and guano from the Pacific Islands, Baker, Jarvis, etc., were 

 chiefly used. From 1871 Mejillones guano began to be used, and 

 then the first difficulties in the manufacture began. The larger fac- 

 tories then installed flatstone mills, roller mills, or stamp mills. This 

 (equipment, however, soon became defective when it was a question 

 of working mineral phosphates such as Canadian or Norwegian 

 apatite. Sombrero, Navassa, Curacoa and Aruba phosphates, Mexican 

 guano, rock phosphate, bone ash, etc. Powerful crushers were 

 then added to the flatstone mills, for it was soon found that fine 

 grinding played an important part in dissolving the phosphate, and 

 in drying the superphosphate. At the same time, the need was 

 felt for a mechanical crusher and sifter for the superphosphate. 

 It was thus that the crusher called Carr's disintegrator was adopted. 



of superior, but is the Latin word super used to show that in superphosphate 

 the ratio of phosphoric acid to the lime is in excess of that in the normal tri- 

 basic phosphate. Super in fact has the same meaning here as in supersaturate, 

 superheat. It has nothing whatever to do with quality. — Tr. 



