12 



The ''other brands" in the same table and immediately following 

 the wood ashes, are two mixtures containing potash and phosphoric 

 acid and were designed for use in connection with cottonseed meal 

 or other like material for growing tobacco. 



Ground Bones. Ground bones used as fertilizer may be divided 

 into two classes, raw and steamed. The former contain more grease 

 and nitrogen than does the steamed or cooked bone which has had 

 the greater part of the grease and some of the nitrogen removed by 

 cooking under pressure. Experiments in the field, however, show but 

 little difference in the agricultural value of equal amounts of plant 

 food in these two materials. The average standard for ground 

 bones, as shown by the analyses made at this laboratory of 253 

 samples, (see compilation of analyses in i8th annual report of this 

 station) is nitrogen 3.06 per cent, total phosphoric acid 24.34 per cent. 



Dissolved Bones. This class of material consists of fine ground 

 bone to which has been added sulphuric acid (oil of vitriol) for the 

 purpose of rendering the phosphoric acid more available. The 

 phosphoric acid in the untreated bone is present in the form of tri- 

 calcium phosphate. In the treatment with sulphuric acid the 

 tri-calcium (three-line) phosphate is largely changed to mono- 

 calcium (one-line) and di-calcium (two-line) phosphate ; the phos- 

 phoric acid in these forms is much more available as plant 

 food than it is in the untreated bone. The average of nine analyses 

 of dissolved bone furnishes the following standard: nitrogen 2.14 

 per cent, total phosphoric acid 16.42 per cent, available phosphoric 

 acid 12.40 per cent. 



Tankage. This material, like the ground bone, is a refuse product 

 from slaughtering establishments. It furnishes a very important 

 source of nitrogen as well as phosphoric acid and large quantities 

 of the various grades of tankage are used in compounding mixed 

 fertilizers. There are several grades known to the trade which may 

 be classed as high, medium and low grade tankages, according to 

 the per cent of nitrogen which they contain. The nitrogen is the most 

 valuable of the essential elements ; for this reason the higher the per- 

 centage present the greater the commercial and agricultural value. 

 The different grades are often designated as 11 and 15 tankage, 9 and 

 20 tankage, 7 and 30 tankage, 6 and 35 tankage etc. meaning 11 

 per cent of ammonia and 15 per cent bone phosphate ; 9 per cent 



