COMPOUND MANUKES. 



149 



into the mixture was of such a nature as to readily lend itself to 

 retrogradation. The causes of this phenomena are of both a 

 physical and chemical nature. The more the superphosphate is 

 distended by ballast, which is here sulphate of ammonia, the more 

 distant the particles are from one another and preserve their con- 

 dition. From a chemical point of view, sulphate of ammonia 

 230ssesses the property of hindering the basic sesquioxides from 

 precipitating themselves, but it is clear that a retrograded super- 

 phosphate cannot be improved by mixture with sulphate of 

 ammonia. 



Tables for the Calculation of Siiperj^hosjjhates of Ammonia. — 

 The first vertical column of Table I gives the content of sulphate 

 of ammonia in per cents of nitrogen, from one-tenth to the next 

 tenth within the limits which are generally met with in practice. 

 The top horizontal column contains the usual percentages in 

 nitrogen of " superphosphates of ammonia," say 2, 3, 4, 5, 6, 7, 8, 

 9 per cent of nitrogen. The figures contained at the points of 

 intersection of these vertical and horizontal columns show the 

 number of cwts. of sulphate of ammonia that must be added to the 

 heaps to get 100 cwts. of the mixture with the desired nitrogen 

 content. Thus, for example, to get a suj)erphosphate of 5 x 10, 

 with 4-9 per cent of nitrogen from a sulphate of ammonia, of 20-2 

 per cent of nitrogen, it is necessary to add for 100 cwts. of mixture 

 sand (!) and superphosphate, including 24 to 25 cwts. of sulphate 

 of ammonia. Table II gives corresponding values for calculating 

 the superphosphates. 



T\BLE XLYI.— SHOWING IN CWTS. THE AMOUNT OF SULPHATE 

 OF AMMONIA OF DIFFERENT STRENGTHS THAT MUST BE 

 CONTAINED IN A 5 TON HEAP TO GET A MANURE CONTAINING 

 FROM 1-850 UP TO o PER CENT NITROGEN. 



