When the industrial sample, more or less voluminous, reaches the laboratory, the chemist is to begin by taking a note of the marks, labels, and descriptions found thereon, and of the nature and state of the package which contains it, and the date of its arrival. All this information should be entered upon the laboratory book and afterwards transcribed on the paper containing the results of the analysis, as well as the name of the person sending it. This having been done, the sample is to be properly prepared in order that a portion may be taken representing exactly the mean composition of the whole. If it is in a state of fine powder, such as ground phosphates and certain other fertilizers, it is sufficient to pass it two or three times through a sieve with meshes one millimeter in diameter, taking care to break up the material each time in order to mix it and to pulverize the fragments which the sieve retains. The whole is afterwards spread in a thin layer upon a large sheet of paper, and a portion is taken here and there upon the point of a knife until about twenty grains are removed, and from this the portion subjected to analysis is afterwards taken. If the sample comes in fragments, more or less voluminous, such as phosphatic rocks or coarsely pulverized guanos containing agglomerated particles, it is necessary first to reduce the whole to powder by rubbing it in a mortar or in a small drug mill. It is next passed through a sieve of the size mentioned above and that which remains upon the sieve pulverized anew until all has passed through. This precaution is very important, since the parts which resist the action of the pestle the 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 heating 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 moisture, both before and after pulverizing, and to calculate the analytical results obtained upon the pulverized sample back to the original sample.