PHOSPHORUS FERTILIZERS 133 



made into sheets and pipes withstands much higher pressure 

 than pure lead of the same weight or thickness. This new 

 material is sometimes used in the construction of leaden 

 chambers and connections. 



The annual production of sulphuric acid in the British 

 Isles before the war was 1,000,000 tons per annum, reckon- 

 ing the acid at 100 %, which is equal to about 1,500,000 tons 

 of chamber acid. In 1918 just under a million tons of 

 chamber acid and 300,000 tons of fuming acid were made in 

 the United Kingdom, both amounts being reckoned at 

 100 % H 2 SO 4 . Since more than 60 % of the nation's acid 

 production is used for fertilizer purposes, the sulphuric acid 

 plants of Great Britain are almost always of the leaden 

 chamber type. Acid plants were often thrown out of action 

 for a time before the war, but during the war period the 

 maximum output was aimed at. 



For some years before the war the manufacture of super- 

 phosphate in this country was unsettled, and there was a 

 gradual decline in the export trade, the maximum having been 

 reached in 1911. The cause of this decline may be chiefly 

 found in the erection of superphosphate plants in countries 

 which have previously imported this material. It must not 

 be forgotten that the British Isles possess no special advan- 

 tages for the manufacture of superphosphate, since both 

 pyrites and phosphate rock have to be imported as raw 

 materials. It was chiefly due to the fact that most super- 

 phosphate works were associated with acid plant that the 

 producers in this country were able to compete with foreign 

 manufacturers. Some of the smaller works found great 

 difficulty in keeping up to date, especially those having to 

 purchase their acid from outside. Owing to the substitution 

 of sulphate of ammonia for nitrate of soda in the British 

 Isles, largely increasing quantities of sulphuric acid have 

 been used in the production of ammonium sulphate. The 

 production of ammonia is likely to increase in this country, 

 and there may be a considerable increase in the demand for 

 sulphuric acid in this direction. On the outbreak of war 

 there was a lack of sulphuric acid, but, since the cessation of 



