THE FARMER'S MAGAZINE. 



229 



wheu they are a complicated mixture of several, which may 

 vary ia their relative proportions, it frequently becomes im- 

 practicable to arrive at any satisfactory result, except by 

 means of a formal analysis. That complexity ia the rule and 

 simplicity the exception with manures, is a matter with which 

 we are all familiar, and hence it will be easily understood that 

 there are substances which, from their very nature, it is im- 

 possible to test. A manure is purchased because it contains 

 certain substances which serve as food for the plants ; but 

 they contain these mixed, in almost every instance, with a 

 large quantity of useless matters, which are there either be- 

 cause they cannot be economically separated, or because they 

 are necessary for the purpose of converting the useful con- 

 stituents into a marketable condition. Thus guano is bought 

 chiefly for the sake of its ammonia and phosphates, and 

 the other matters are of little or no value, but, as they 

 cannot be separated, must be taken by the purchaser; 

 and so likewise sulphate of ammonia is bought for the am- 

 monia it contains, and the sulphuric acid has little if any 

 manurial value, but cannot be dispensed with, as it renders 

 the ammonia transportable without loss. When the value 

 of manure is determined by one only of its constituents, 

 as is the case with sulphate of ammonia and some few other 

 substances, it is comparatively easy to ascertain whether 

 they are genuine or not ; but when they contain several such 

 substances, which may vary within very wide limits in their 

 relative proportions, the difficulty becomes materially en- 

 hanced, and it is necessary to depend upon tests which do 

 not always afford conclusive proof, but rather tend to awaken 

 suspicion. When it is further added that many manures 

 contain naturally small quantities of the very substances most 

 likely to be employed for adulterating them, we see additional 

 reasons why it cannot always be practicable to ascertain with 

 certainty, by the use of tests alone, whether a manure is 

 genuine or not. In point of fact, we know that all guanos 

 contain saud, most of them common salt, and particular va- 

 rieties contain sulphate and carbonate of lime, and these sub- 

 stances are almost the only ones which are used for adulterat- 

 ing that manure. It must be obvious, from what has been 

 said, that the testing of manures requires some judgment, and 

 cannot be reduced to a perfectly mechanical system. It depends 

 indeed, in no small number of cases, upon the observation of 

 what may at first sight appear very trifling matters ; but they 

 are such as are easily mastered by any one who has the habit 

 of observing, and is inclined to take advantage of any oppor- 

 tunities he may meet with of examining samples, so as to give 

 him confidence in the accuracy of his own results. In pro- 

 ceeding to point out the mode of detecting adulterations in 

 the individual substances used as manures, I shall commence 

 with those which are of simple composition, and proceed 

 gradually to those of greater complexity. I shall select, as 

 the first, sulphate of ammonia, because it is a substance which 

 presents no diflicultiesiu testing. Supposing a person were 

 desirous of ascertaining the purity of a sample of that manure, 

 he will proceed, in the first instance, to note its colour ; and if 

 that be pale, and it be made up of distinctly crystalline frag- 

 ments, he will have, at all events, one favourable character on 

 which to depend ; but even if it be dark coloured, he will not 

 hurriedly infer that it is not genuine, although he will natu- 

 rally direct greater attention to all the other points of the ex- 

 amination. He will next see that it is uniform iu colour 

 throughout^ for if it contains white grains or lumps, obviously 

 different from the greater part of the mass, he will be entitled 

 to suspect that it is a mixture ; and in order to make sure of 

 this, he may pick out a few pieces, taste them.and reserve some 

 more for further experiments. He may then take a quantity 

 of the substance, spread it upon a piece of blotting paper, and 

 inverting a saucer or small box over it, leave it for some hours. 

 If at the end of that time the blotting paper has become 

 very damp, the sample probably contains more than the 

 usual quantity of moisture. The next process consists in 

 placing a small quantity of the sulphate upon a fire-shovel, 

 or better still, in a small porcelain capsule or cup, such as 

 I now show you, and placing it over a clear fire until it 

 ceases to give off fumes. If pure it will almost entirely vola- 

 tilise, and leave behind only a very small quantity of sand or 

 other fixed matters. A genuine sample of sulphate of ammo- 

 nia contains from 94 to 97 per cent, of the pure salt, and rarely 

 more than 1 per cent, of non-volatile matters, so that the resi- 

 due in this experiment ought to be very small. If the sample 



stands all these teats it may be considered genuine, but it 

 must be particularly noticed that it may contain a considera- 

 bly smaller quantity of sulphate without these testa unequivo- 

 cally indicating the fact, but it would still be genuine although 

 inferior in quality ; and it must be distinctly understood once 

 for all, that tests do not enable us to distinguish the relative 

 qualities of difl'erent samples where all are genuine. For this 

 purpose analysis is absolutely necessary, and its importance 

 will be understood when it ia borne in mind that a diminution 

 of only 1 per cent ia the quantity of ammonia corresponds to 

 a reduction in value of nesrly ISs. per ton. The observations 

 just made regarduag the sulphate are equally applicable to the 

 muriate of ammonia; but as that substance is rarely employed 

 as a manure, and is more expensive than the sulphate, over 

 which it has no advantages, it is perhaps scarcely necessary to 

 refer to it. It is necessary, however, for me to guard against 

 the application of these tests to a substance sold as inurio- 

 sulphate or sulphc-muriate of ammonia. That manure is ob- 

 tained during a particular manufacturing process, and always 

 contains a larger quantity of fixed salts, and must not on that 

 account be considered as adulterated ; although, from the very 

 nature of the process by which it is prepared, its quality must 

 necessarily be very variable. It wiU be noticed that the vola- 

 tility of the salts of ammonia is the most valuable means of 

 determining their purity, and it ia important because it is an 

 unusual character; and if they be adulterated at all, it is only 

 fixed substances, such as common salt, which can be employed : 

 and hence it is advisable, when the sample does not appear 

 uniform, to pick out what seems to be foreign matters, and to 

 heat them separately for the purpose of ascertaining whether 

 they are volatile. The next manure to which I shall refer is 

 the nitrate of soda, which has peculiar claims upon our atten- 

 tion ; for though the numbers of substances which can be used 

 for adulteratmg it is extremely restricted, it invariably con- 

 tains common salt iu greater or less quantity. The source of 

 this impurity depends upon the mode in which nitrate of soda 

 occurs. Every one is aware that it is imported from Peru 

 (though commonly called Chili saltpetre), but it is not gene- 

 rally known that it is there found in beds containing from 40 

 to 80 per cent., along \<ith small quantities of common salt 

 and other impurities, and is prepared for the market by treat- 

 ing the matter removed from the beds with water, and then 

 evaporating until crystals are deposited. By this process 

 the larger proportion of the salt is separated ; but a certain 

 quantity, dependent upon the amount of care which has 

 been exercised, is always left ; and hence, even where adul- 

 teration is not suspected, it becomes of importance to be 

 able to determine the quality of the article purchased. 

 Nitrate of soda, like sulphate of ammonia, possesses the in- 

 valuable characteristic of a crystalline texture, which precludes 

 the use of most mixtures, insomuch so that there are really 

 only common salt, and possibly sulphate of soda, which could 

 be mixed with it. The use of the latter is, however, very un- 

 likely, because, as usually met with in commerce, its appear- 

 ance is very different from that of the nitrate of soda, and 

 could scarcely be mixed with it without exciting suspicion. 

 In examining a specimen of nitrate of soda, the farmer will 

 naturally direct attention, in the first instance, to its dryness, 

 which he endeavours to determine in the same manner as has 

 been recommended for sulphate of ammonia. He will then look 

 to its general appearance, which he will expect to find extremely 

 like that of raw sugar, being composed of small grains whicli 

 should be uniform iu appearance, and have a browuiah, but 

 not too dark a colour. If the eye distinctly detects a mix- 

 ture of two kinds of grain, one whiter than the other, the pre- 

 sence of common salt as an adulteration may be suspected ; 

 and if some of the whiter grains separated from the mass 

 prove to have a purely saline taste, the probability of this is 

 increased. As most of the commercial forms of common salt 

 are much whiter than nitrate of soda and have never a brown 

 tint, the importance of attending to this poiot will be obvious ; 

 but it must be understood that the appearance of a few white 

 grains is of no importance, especially if their taste differ from 

 that of salt. The presence of common salt is easily detected 

 by means of a solution of nitrate of silver (or lunar caustic), 

 which immediately produces a curdy white deposit in any 

 fluid containing it. But the mere appearance of this precipi- 

 tate is no proof that the nitrate has been adulterated, for I 

 have here a solution of a perfectly genuine specimen, which, 

 as you perceive, immediately gives it. If any use ia to be 



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