20 AGRICULTURAL ANALYSIS 



25. Method of the International Commission. The methods 

 adopted by the international commission are as follows : 



(a) Dry samples of phosphates or other artificial manures may 

 be simply sifted and then mixed. 



(b) In the case of damp materials, where the above procedure 

 is not possible, the preparation must be confined to a careful mix- 

 ing by hand. 



(c) In the case of raw phosphates and animal charcoal, a water 

 determination is to be made, as confirmatory evidence. 



(d) In dealing with substances which are apt to lose water 

 during grinding, the moisture is to be determined both before and 

 after the preparation of the sample, the results of the analysis 

 being afterwards calculated back into the original hygroscopic 

 condition of the sample as received. 



26. Method of the French Agricultural Stations. The man 

 ner of proceeding recommended by the French stations varies 

 with the fertilizer. If it is not already in the form of a 

 powder it is necessary to pulverize it as finely as possible by rub- 

 bing it up in a mortar. In certain cases, as with superphos- 

 phates, the material should be passed through a sieve having 

 apertures of one millimeter diameter, all the larger parts being 

 pulverized until they will pass this sieve. 



When the matters are too pasty to be divided in the mortar 

 they should be divided by means of a knife or a spatula. They 

 should then be incorporated with a known weight of inert, pul- 

 verulent matter such as fine sand, with which they should be 

 thoroughly mixed and in subsequent calculations the quantity 

 of sand or other inert matter added must be taken into consid- 

 eration. Usually a pasty state of a fertilizer is due to the 

 humidity of the mixture. In this case a considerable volume of 

 the sample is dried and then reduced to a pulverulent state. 

 In the subsequent calculations, however, the percentage of mois- 

 ture lost must be taken into consideration. 



Before drying a sample it is necessary to take into considera- 

 tion whether or not the product will be modified by desiccation 



9 Grandeau, Trait d' Analyse Matieresdes agricoles, 3rd Edition, 1897, 

 1 =409. 



