72 Detection of Adulterations. 



accurate index of its dilution ; but few persons have the necessary 

 apparatus, and the preceding process is at once easier and more than 

 sufficiently accurate. 



Ammonia. — Among the impurities sometimes found in the liquid 

 ammonia of commerce, is a portion of oil derived from the animal 

 matter used in the early stages of its preparation. If ammonia be 

 very cautiously mixed with a great excess of concentrated sulphuric 

 acid, the presence of oil will, after some time, be indicated by the 

 evolution of charcoal. The presence of hydrochloric acid may be 

 discovered by saturating a portion of the alkali with pure nitric acid, 

 and then adding a solution of nitrate of silver, which will give a pre- 

 cipitate of chloride of silver, if any of the suspected acid be pres- 

 ent. Sulphuric acid is detected in ammonia, by saturating the alka- 

 li with pure nitric acid, and then adding any solution of barytes ; if 

 a precipitate occur, the alkali contains a sulphate. It is necessary 

 to add the nitric acid in the first place, because a precipitate would 

 otherwise occur from the presence of a little carbonate of ammonia, 

 which the liquid of commerce almost always contains. The strength 

 of the volatile alkali is greater in proportion to its lightness and the in- 

 tensity of its odor. 



Arrow-Root. — This substance is sometimes largely adulterated 

 with starch, and the fecula of potatoes. The color however, of 

 arrow-root, is less white than that of the two latter substances, its 

 grains are much finer, and when examined with a magnifying glass 

 appear pearly and very brilliant. It also contains small lumps, which 

 very easily crumble between the fingers. Finally, the jelly made 

 from arrow-root and water is inodorous ; while the other substances 

 have a very distinct smell. Such are the distinctive characters given 

 by our authors, and it is important to observe them. 



Proto-chloride of Mercury, Calomel. — This substance, when pure, 

 is entirely volatilized by heat ; any fixed residue being an impurity. 

 As, however, it is liable to contain a little corrosive sublimate, which 

 is also volatile, and which would be a very dangerous contamina- 

 tion, it is proper to state the process by which that poison may be 

 detected. Digest a portion of calomel with four times its weight ot 

 rectified alcohol, at a moderate heat ; filter the alcohol, then dilute 

 it with an equal weight of water, and add lime-water. If the cor- 

 rosive sublimate be present, a reddish precipitate* will be formed. 



Rather a yellowish red. It is difficult to name the color. 



