228 



THE FARMER'S MAGAZINE. 



"ON THE METHODS BY WHICH THE 

 FARMER CAN BEST PROTECT HIM- 

 SELF FROM THE ADULTERATION OF 

 MANURES" : 



A LECTURE BY PROFESSOR ANDERSON, 



Delivered during tlie Higlil.md and Agricultural Society's 

 meetiug at Glasgow. 



The Honourable the Lord Frovost occupied the chair, and 

 iutroduced the lecturer in a few appropriate sentences. 



Professor Anderson aaid: Although no one will doubt 

 the imrortance of the subject selected for my address on the 

 present occasion, many persons may be inclined to think that 

 it has so frequeutly been brought under the notice of the 

 farmer that it must be considered in some respects exhausted, 

 and that I am only about to go over the beaten track, and to 

 repeat once more what has been already frequently and better 

 said by others. I trust, however, it will be at once apparent that 

 the points to which I propose to direct your attention possess at 

 least some deeiree of novelty, and may lead to useful practical 

 resuha, in so far as it is my intention to endeavour to teach the 

 farmer how he may rely upon himself for detecting the more 

 frequent and obvious adulterations to which manures are sub- 

 ject, for checking to a certain extent the correspondence between 

 the substance he buys and the analysis by which it was sold, 

 and to show that there are means by which this can be effected 

 in particular cases with considerable certainty, and without 

 any material difficulty; in short, I propose to show the extent 

 to which the farmer may make himself independent of the 

 chemist in determining the grosser adulterations of manures, 

 and to lay down some definite rules by which any person may 

 detect them ; and at the same time to set bounds to his self- 

 reliance, by directing attention to the (act that, though it may 

 often be possible for him to resort with success to simple ob- 

 servations and experiments, there are also numerous instances 

 demanding an amount of skill and experience which each indi- 

 vidual cannot be expected to acquire for himself. No one who 

 is at all conversant with tbe way in which manures are too 

 often purchased will fail to recognise the importance of such 

 knowledge, or can doubt that a greater familiarity with the 

 distinctive characters of different manures would lead to the 

 detection of many cases of adulteration which now pass unno- 

 ticed; and as these occur most commonly in small purchases, 

 when it is not thought necessary to have recourse 

 to analysis, the loss falls most severely upon small 

 farmers, who are the class least able to bear it. 

 Persons of extensive experience, and who are in 

 the habit of frequently examining manures, are generally so 

 familiar with the appearance of genuine samples that their 

 suspidon is excited by anything unusual; but even they may 

 be often misled ; for the eye is a very fallacious guide, and 

 adulterators know but too we'd that it is easy to uiialead those 

 who rely upon it, and hence it becomes necessary to call in the 

 ail of some simple tests for the purpose of disclosing what the 

 unassisted bcnses do not enable us to detect. If these diffi- 

 culties are encouuti.red by those whose attention is constantly 

 directed to the quality of manures, the position of a farmer 

 who once a-year buys the small quantity he requires becomes 

 intelligible, and the advantage he would derive from a precise 

 knowledge of the appearance of genuine manures, and still 

 more from the possession of simple modes of detecting im- 

 purities, may be easily conceived. That such knowledge may 

 be acquired by the farmer I am fully convinced, but at the 

 same time the difficulties which attend it must not bo over- 

 looked, and it is peculiarly necessary for me to guard against 

 misapprehension in this respect, and to bring prominently for- 

 ward, in the most distinct language, the points in regard to 

 which we must expect to meet with uncertain or deceptive re- 

 sults. The principal difficulty which besets the whole subject 

 lies in the complexity of such manures and the absence of dis- 

 tinctive characters, which either form a bar to adulteration, or 

 at least limit the number of substances which can be used for 

 that purpose without detection. The great importance of such 

 properties may be illustrated by reference to some familiar 

 aubatauce, such, for instance, as loaf-sugar, which, as wc at 



once see, would have to be adulterated with some substance o* 

 very peculiar properties ; for not only must it be white and 

 tasteless, but it must possess that peculiar granular crystalline 

 texture which we see in loaf-sugar, and also be capable of 

 adding to the grains of sugar in such a manner that the whole 

 may be made up into loaves ; and as there is no cheap sub- 

 stance possessing these properties, the adulteration of loaf- 

 sugar is a practical impossibility. But it is different if the 

 sugar is sold ground, or in the form of sugar-plums ; for then 

 the crystalline texture, which is so invaluable a characteristic 

 and so incapable of imitation, is lost, and any white 

 powder may be mixed with it without detection ; 

 and hence chalk, gypsum, and other substances, are 

 actually used for this purpose. It will at once occur to 

 every one that these substances may be detected by throw- 

 ing the mixture into water, when the sugar dissolves, and 

 leaves the adulterating matei-ial in the fonn of a white 

 powder at the bottoni of the vessel. By means of this 

 simplii experiment we test the purity of the siabstance 

 examined ; and it is my intention to explain the nature of 

 similar, though not always equally simple, methods of exa- 

 mination, which are applicable to some of the more common 

 manures. In order that the amount of information which 

 it is possible for an individual to acquire for himself may 

 be fully understood, it is necessary for me, in the first place, 

 to point out the difference between testing and analyzing a 

 substance, in regard to which much misapprehension exists; 

 and this may be most easily done by means of a single 

 experiment, which will save much circumlocution. I have 

 here two glasses containing water, and supposing we are 

 desirous of ascertaining whether they contain lime in 

 solution, it is only necessary to add to both a small 

 quantity of this solution, which contains a substance 

 called by chemists the oxalate of ammonia, when it 

 is found that the one remains clear and the other 

 becomes muddy, because the lime it contains is made 

 to pass into the form of an insoluble white powder, 

 wich soon deposits, or, ns we say in chemical 

 language, precipitates to the bottom of the fluid. In this 

 experiment we have obtained a result which enables us to 

 assert, with the most absolute certainty, that lime exists in 

 one of these fluids ; and we have applied a test and thus 

 proved its presence, although we have obtained no informa- 

 tion as to its quantity. It is possible, indeed, when two 

 fluids are compared with one another, to form a rough esti- 

 mate from the amount of muddiness, and to say that the 

 one contains a large and the other a small quantity of lime; 

 but the conclusion arrived at in this way would be very 

 imperfect and fallacious ; and where definite information 

 is required on this point, it is necessary to proceed on a 

 different principle, and by means of an experiment which 

 cannot be shown here, for it extends over many hours, to 

 determine the exact quantity. When this is done, we are 

 said to have made an analysis ; and the difference between 

 testing and analyzing a substance lies in this — that the 

 latter deals with quantities, and is therefore more precise 

 and complete, while the former indicates only the presence 

 or absence of some particular constituent. It is obvious, 

 however, that, provided we know the impurities likely to 

 be met with in any article, it is only necessary to make use 

 of the tests by which they are distinguished, and if we 

 prove their absence we at once substantiate the purity of 

 the substance examined. In making this experiment we 

 go upon the assumption that the article when genuine must 

 he perfectly free from all foreign matters ; but in actual 

 practice it is found that very few commercial articles are in 

 this predicament, but are generally supplied only in a state 

 of approximative purity, and we are not entitled to con- 

 demn a substance as adulterated merely because the test 

 indicates an impurity ; but it becomes necessary so far to 

 modify the mode of testing as to make allowance for the 

 quantity of foreign matter which may be reasonably expected 

 to exist in the article, and a more complicated system of 

 testing must be employed. In point of fact, the process must 

 partake, to a certain extent, of the nature of au analysis, and 

 must of necessity in some cases acquire a degree of complexity 

 which places it beyond the power of anyone except those who 

 have acquired some chemical knowledge. Still, where the 

 article consists, or ought to consist, entirely of one single 

 substance, these difficulties are far from insurmountable ; but, 



