M.—AGRICULTURE 255 
potash in suitable proportions and all soluble in water. The basis of 
these fertilisers is a mono-ammonium phosphate which is made by 
subjecting finely ground rock phosphate to the action of a mixture of 
sulphuric acid and ammonium sulphate. This gives directly a solution 
of mono-ammonium phosphate containing a little ammonium sulphate 
and calcium sulphate is precipitated. ‘The mono-ammonium phosphate 
contains 12-2 per cent. nitrogen and 61-7 per cent. phosphoric acid and 
is thus a highly concentrated fertiliser. By mixing this with ammonium 
sulphate and a suitable potash salt, a wide range of fertilisers can be 
obtained. ‘The ingredients are finely ground and then passed to a special 
incorporator in which they are churned by means of paddles, whilst 
saturated steam is blown in. In this way, granules are formed which 
are then dried ; roughly, one ton of such fertilisers supplies as much 
plant food as two tons of the ordinary mixed fertiliser of similar com- 
‘position. They possess the obvious advantage of reducing freight and 
handling charges and cost of distribution to the land ; they are granular 
in texture and very easy to sow, and they can be stored without risk 
of deterioration ; further, the constituents are all soluble in water. 
Another point claimed in their favour is that they contain little except 
the three fertilisers, nitrogen, phosphates and potash, while the ordinary 
fertilisers contain appreciable, and in some cases large, amounts of calcium, 
sulphur, and other elements. It is possible that in some soils the absence 
of the additional substances might be a disadvantage, and a careful com- 
parison of the new fertilisers with the old mixed fertilisers will be necessary 
_to show that no disadvantage attends the use of the new compounds over 
a number of years. Accurate field experiments on a wide variety of soils 
were carried out in this country in 1930 to compare the relative effects 
of the concentrated complete fertilisers and of mixtures of sulphate of 
ammonia, superphosphate and potash giving the same amounts of nitrogen, 
phosphates and potash. With the three crops examined (oats, potatoes 
and sugar beet), the concentrated fertilisers gave the same average increases 
in yield as the equivalent ordinary mixtures. At certain centres, however, 
the concentrated fertilisers gave better results and at others a poorer yield 
than the ordinary mixtures. The work is being continued. 
It is obvious that if the concentrated fertilisers were used continuously 
over a number of years, increased attention would require to be given to 
liming. 
BIOCHEMISTRY. 
When we consider the development of organic chemistry during the 
past century, we see that the earlier workers were much occupied with 
the investigation of the substances which occur naturally in plants and 
animals ; although many individual organic substances were known before 
this time, the modern developments of organic chemistry may be said to 
date from Wohler’s memorable syntheses of oxalic acid in 1824 and of 
urea in 1828. While the early organic chemists were much interested in 
those compounds which occur in plants and in the animal body, the trend 
of investigation, particularly in this country, then shifted to the investi- 
gation of more theoretical questions, e.g. the investigation of radicles, 
