MIXED FERTILIZERS 15 



ing agglomerated particles, it is necessary first to reduce the 

 whole to powder by rubbing it in a mortar or by using a small 

 drug mill. It is next passed through a sieve of the size men- 

 tioned above and that which remains upon the sieve pulverized 

 anew until all has passed through. This precaution is very im- 

 portant, since the parts which resist the action of the pestle most 

 have often a composition different from those which are easily 

 broken. 



When the products to be analyzed contain organic materials, 

 such as horn, flesh, dry blood, etc., the pulverization is often a 

 long and difficult process, and results in a certain degree of heat- 

 ing, which drives off some of the moisture in such a way that the 

 pulverized product is at the last drier, and, consequently, richer 

 than the primitive sample. It is important to take account of this 

 desiccation, and since the pulverization of a mass so voluminous 

 can not be made without loss, the determination of the total weight 

 of the sample before and after pulverization does not give exact 

 results. In such a case it is indispensable to determine the mois- 

 ture both before and after pulverizing, and to calculate the analyt- 

 ical results obtained upon the pulverized sample back to the orig- 

 inal sample. In order to escape this necessity, as well as the diffi- 

 culties resulting from the variations in moisture during transpor- 

 tation, some chemists have thought it better to always dry the 

 commercial products before submitting them to analysis, and to 

 report their results in the dry state, accompanied by a determina- 

 tion of the moisture, leaving thus to the one interested the labor 

 of calculating the richness in the normal state, that is to say, in 

 the real state in which the merchandise was delivered. 



In addition to the fact that this method allows numerous 

 chances of errors, many substances undergoing important changes 

 in their composition by drying alone, it has been productive of 

 the most serious consequences. The sellers have placed their 

 wares on the market with the analysis of the material in a dry 

 state, and a great number of purchasers have not perceived the 

 fraud concealed under this expression so innocent in appearance. 

 It is thus that there has been met with in the markets guano con- 

 taining twenty-five per cent, of water, which was guaranteed to 



