234 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



3. The forms of combination in which the valuable ingredients occur, 

 and their consequent agricultural values. 



4. Some of the ways in which the fertilizers may be improved, and 

 their values increased. 



In the consideration of these topics, which must be brief, some data 

 will be used which may be found in more detail in previous articles 

 and reports by the writer. * 



Explanations of chemical terms used in fertilizer analyses. 



307. The following explanations of terms used in fertilizer analyses 

 will be of use to those not familiar with such subjects : 



Moisture. — AH fertilizers contain more or less water, which, of 

 course, has no commercial value, and serves to make them heavier and 

 relatively poorer in valuable ingredients. In the analysis, that which is 

 removed by heating to 212° Fahrenheit (or, in some cases, to a some- 

 what higher temperature) is designated as moisture. By subjecting 

 the dried material to a higher temperature, the organic and volatile mat- 

 ters are driven off, and the ash remains. By treating this ash with 

 strong acids, all that is of any value is dissolved. 



Sand and insoluble matters. — The residue, which resists the 

 action of both lire and strong acids, consists of silica and other mineral 

 matters. These possess no fertilizing value, and are classified as sand, 



i&C. 



isiTROGEN. Ammonia.— In our ordinary fertilizers much or all of the 

 nitrogen exists in unavailable forms. By more or less rapid alter;)tions, 

 by decay or otherwise, which take place in the soil, these are changed to 

 other compounds, which the plant can readily use as food. Of these lat- 

 ter, nitric acid, wiiich contains nitrogen combined with oxygen, is one ; 

 ammonia, which consists of nitrogen and hydrogen, and is represented 

 by the chemical formula NH3, is another. Fourteen parts by weight of 

 nitrogen unite with 3 parts of hydrogen to form 17 parts of ammonia. 

 Accordingly, 14 parts of nitrogen are said to be equivalent to 17 of am- 

 monia, or what is the same thing, 100 parts of nitrogen are reckoned as 

 equivalent to 121 parts of ammonia. In })ure sulphate of ammonia all 

 the nitrogen is in the form of ammonia. In Peruvian guano some of the 

 nitrogen exists as ammonia also. In our other ordinary fertilizers there 

 is little or no ammonia. The very common practiceof reckoning nitrogen 

 as ammonia in fertilizers which do not contain it in this form is incorrect, 

 misleading, and therefore wrong, and ought to be abolished. 



Ammonia combined with sulphuric acid forms sulphate of ammo- 

 nia; nitric acid combined with soda forms nitrate of soda. 



Phosphoric acid: soluble, reverted, and insoluble. — By 

 phosphoric acid is understood the compound of [)hosphorus and oxygen 

 which is represented by the chemical formula P2O5, or PO5. This, com- 

 bined with lime, forms phosphate of lime. The phosphate of lime which 



* See particularly report of Couu. Agl. Expt. Station in Report of Conn. Board of 

 Agriculture for 1876. 



