MANURES AND MANURING I749 



Extraction of iodine and bromine. — Inorganic iodides and bromides 

 are easily obtained from kelp by simple lixiviation with weak acid or wa- 

 ter. Organic compounds of iodine and bromine on the other hand cannot 

 be completely extracted without destroying the mucilaginous residue 

 unless an oxidising agent be employed in a faintly acid solution, according 

 to the process patented in various countries (France, Germany, Austiia, 

 Belgium, England, Norway, United States and Japan). 



1262 - Green Manuring with Leguminous Crops in Java. — Rant a., in Medcdeeimgcn 



van het Kina Proef station, No. III. Batavia, 1915. 



At Tjinjiroen, in the mountainous region of Java, experiments were 

 carried out on the growth of various leguminous crops for green manure. 

 The trial ground was 5160 ft. above sea level. An account is given of the 

 plants tested with special reference to the formation of root nodules and to 

 the appearance of disease. 



1263 - The Solubility of Phosphoric Acid in Mineral, Basic and Calcined Phosphates, 



and in Basic Slag. — Aita a., in i:it«lia AgncuUi, Year lyV, No. 10, pp. 446-453. I'ia- 



cenza, October 15, 19 16. 

 Since the middle of the nineteenth century phosphatic manures have 

 been employed chiefly as superphosphate and basic slag. In recent years, 

 however, attempts have been made to re-introduce the use of natural 

 phosphates in one of the three following forms : i) ground phosphate which 

 consists of the raw mineral reduced to a very fine state of division ; 2) cal- 

 cined phosphate or " thermophosphate " which is the mineral phosphate 

 after simple calcination ; and 3) basic phosphate, a product obtained by 

 calcining the raw mineral with basic or alkaline substances. The writer 

 has studied the solubility of mineral phosphates, more especially the less 

 soluble ones, {Annali di Chimica applicata, July and August 1916) and 

 gives a summary of his work in the present paper. 



Mineral phosphates. — Recent experiments have shown that : 

 i) The power of assimilating phosphoric acid from mineral phos- 

 phates varies with the species of the plant, being marked in crucifers and 

 hardly perceptible in cereals. 



2) A very fine state of division increases the availability of mineral 

 pho.sphates. 



3) With phosphates in general, and particularly with the less .solu- 

 ble phosphates, the manurial value is dependent on : a) the lime content 

 of the soil ; b) the nature of the nitrogenous manure ai)plied with the phos- 

 phate ; c) the magnesium content of the soil. These three factors are referred 

 to as the calcium, lime and magnesium factors. 



It has been maintained that the slow availability of phosphoric acid 

 in mineral phosphates is reflected in a low solubility in 2 per cent citric 

 acid solution ; but this hypothesis has since been disproved, it being shown 

 that mineral phosphates yield the whole of their phosphoric acid to 2 per 

 cent citric acid provided a sufficient amount of the solvent be used and the 

 extraction be continued for a sufficient length of time. The writer subjected 

 different types of phosphates (Tunisian, Algerian, Florida and Pacific) 



