22 AGRICULTURAL ANALYSIS 



left in a cool place for at least a quarter of a year from the time 

 of its reception, in order that it may be subjected to any sub- 

 sequent investigations which may be demanded. 



(4) In the case of raw phosphates and bone-black the amount 

 of water which they contain should be determined at from 105 to 

 1 10. Samples which in drying lose ammonia in any way, should 

 have this ammonia determined. 



(5) Samples which are sent to other laboratories for control 

 analyses should be securely packed in air-tight glass bottles. 



(6) The weight of the samples should be entered in the 

 certificates of analysis. 



(7) Samples which, on pulverizing, change their content of 

 water, must have the water content estimated in both the coarse 

 and powdered condition and the results of the analysis must be 

 calculated to the water content of the original coarse substance. 



28. Special Cases. Many cases arise of such a nature as to 

 make it impossible to lay down any rule which can be followed 

 with success. As in almost every other process in agricultural 

 chemistry, the analyst in such cases must be guided by his judg- 

 ment and experience. Keeping in view the main object, viz., to 

 secure in a few grams of material a fair representation of large 

 masses, he will generally be able to reach the required result by 

 following the broad principles already outlined. In many cases 

 the details of the work and the adaptations necessary to success 

 must be left to his own determination. In all special cases the 

 methods of securing the samples should accompany the analytical 

 data. 



DRYING SAMPLES OF FERTILIZERS 



29. Difficulties of Desiccation. The determination of the un- 

 combined moisture in a sample of fertilizer is not an easv 

 task. In some cases, as in powdered minerals, drying to con- 

 stant weight at the temperature of boiling water is sufficient 

 In organic matters containing volatile nitrogenous and other com- 

 pounds these must first be fixed by oxalic or sulfuric acid, before 

 the desiccation begins. If any excess of sulfuric acid be added, 

 however, drying at 100 becomes almost impossible. Particular 

 precautions must be observed in drying superphosphates. In 



