Sir John Bennet Lawes. 229 



number of substances was being discovered at this time, and, in order 

 to make these substances, I sowed on my farm poppies, hemlock, 

 henbane, colchicum, belladonna, etc. Some of these are still growing 

 about the place. Dr. Thomson had suggested a process for making 

 calomel and corrosive sublimate by burning quicksilver in chlorine gas. 

 I undertook to carry out the process on a large scale, and wasted a good 

 deal of time and money on a process which was, in fact, no improve- 

 ment on the process then in use."* At this time Dr. Anthony Todd 

 Thomson, Professor of Materia Medica at University College, London, 

 was his chief instructor and adviser. An old barn at Rothamsted was 

 transformed into a laboratory, and here the calomel was afterwards 

 made; this laboratory remained in active use till 1855. 



The researches of De Saussure, on the nutrition of plants, seem to 

 have first called Mr. Lawes' attention to the relations between chemistry 

 and agriculture. In 1837 he commenced experiments in pots with 

 agricultural plants, the manures made use of supplying various elements 

 of plant food. These experiments were continued on a larger scale in 

 1838 and 1839. Spent animal charcoal was then a waste product, and 

 Mr. Lawes was asked by a London friend if it could be turned to any 

 use. He therefore employed it as a manure in his pot experiments, 

 and discovered that if previously treated with sulphuric acid its 

 efficacy as a manure was greatly increased. Apatite and other mineral 

 phosphates were soon treated in a similar manner, and the " super- 

 phosphate of lime," thus prepared, was found to be most effective as a 

 manure, especially for turnips. The new superphosphate was employed 

 on a large scale for crops on the Eothamsted farm in 1840 and 1841, 

 and the results were so satisfactory that in 1842 Mr. Lawes took out a 

 patent for the manufacture of superphosphate. 



The application of sulphuric acid to bones had been practised before 

 the date of Mr. Lawes' patent ; the novelty of his patented invention 

 consisted in the treatment of mineral phosphates in this manner. The 

 supply, of bone available for farmers is but small, but the supply of 

 apatite, coprolite, and of the various rock phosphates discovered in 

 recent years, is almost unlimited. These mineral phosphates are 

 usually too insoluble to have any practical value as manure, but by 

 treatment with a limited quantity of sulphuric acid, a mixture of 

 monocalcic phosphate, phosphoric acid, and gypsum is produced. The 

 phosphates in this compound are almost entirely soluble in water, and 

 far more efficacious as manure than the phosphates of raw bone. The 

 enormous influence which the introduction of superphosphate has had 

 on the development of agriculture may be gathered from the quantity 

 now annually employed by farmers. The annual manufacture of 



* " Agricultural Gazette," January 2, 1888. 



