ACONITUH 



25 



used for acidimetrical purposes, proceed as follows : Fill bottle A with ordinary oil 

 of vitriol to about one-half of its capacity, and pour into bottle B the accurately 

 "weighed quantity of acid to be examined, namely, 

 9-1 grains for sulphuric acid, 12-27 for nitric acid, 

 &c. &c., according to the rule and table given 

 (page 24), and dilute it with water, so that bottle 

 B may be one-third full. Put now into a test- 

 tube a quantity of bicarbonate of soda sufficient 

 to saturate the weight of acid contained in bottle 

 B, and suspend it into that bottle by means of 

 a thread, kept tight by the pressure of the cork. 

 Weigh now the whole apparatus accurately ; this 

 done, carefully loosen the thread, so that the test- 

 tube charged with bicarbonate of soda may fall 

 into the acid, and the cork being instantly ad- 

 justed air-tight, the whole of the carbonic acid 

 gas disengaged is led by tube c into the concen- 

 trated sulphuric acid of bottle A, which absorbs 

 all its moisture before it finally escapes through 

 the tube a. When all effervescence has ceased, 

 the operator, by applying his lips to that tube a, 

 sucks out all the residuary carbonic acid gas con- 

 tained in the apparatus, and replaces it by at- 

 mospheric air, which enters at d. The apparatus, 



if it have become warm, should be allowed to cool completely, and on weighing it 

 again the loss indicates the per-centage of real acid present in the sample. 



The balance used in these methods should, of course, be sufficiently delicate to 

 indicate small weights when heavily laden. 



We shall terminate this article by a description of Liebig's acidimetrical method of 

 determining the amount of prussic acid contained in solutions ; for example, in medi- 

 cinal prussic acid, in laurel and bitter-almond water, essence of bitter almonds, and 

 cyanide of potassium. The process is based upon the following reaction : When an 

 excess of caustic potash is poured into a solution which contains prussic acid, cyanide 

 of potassium is, of course, formed ; and if nitrate of silver be then poured into such a 

 liquor, a precipitate of cyanide of silver is produced, but it is immediately redis- 

 solved by shaking, because a double cyanide of silver and of potassium (Ag Cy + 

 K Cy) is formed, which dissolves, without alteration, in the excess of potash em- 

 ployed. The addition of a fresh quantity of nitrate of silver produces again a 

 precipitate which agitation causes to disappear as before ; and this reaction goes on 

 until half the amount of prussic acid present in the liquor has been taken up to 

 produce cyanide of silver, the other half being engaged with the potassium in the 

 formation of a double cyanide of silver and of potassium, as just said. As soon, 

 however, as this point is reached, any new quantity of nitrate of silver poured in the 

 liquor causes the cyanide of potassium to react upon the silver of the nitrate, to pro- 

 duce a permanent precipitate of cyanide of silver, which indicates that the reaction is 

 complete, and that the assay is terminated. The presence of chlorides, far from inter- 

 fering, is desirable, and a certain quantity of common salt is accordingly added, the 

 .reaction of chloride of silver being analogous to that of the cyanide of the same metal, 



To determine the strength of prussic acid according to the above process, a test or 

 normal solution should be first prepared, which is as follows : 



Since 1 equivalent of nitrate of silver ( = 170) represents, as we have seen, 2 

 equivalents of prussic acid ( = 54), dissolve, therefore, 170 grains of pure fused nitrate 

 of silver in 10,000 water-grains' measure of pure water ; 1,000 water-grains' measure 

 (1 acidimetor full) of such solution will therefore contain 17 grains of nitrate of 

 silver, and will therefore represent 5'4 grains of prussic acid ; and consequently each 

 acidimotrical division 0-054 grain of pure prussic acid. 



ACIPEKTSER. A genus of cartilaginous ganoid fishes, to which the Sturgeon 

 belongs, and from which isinglass is obtained. The roe of the sturgeon yields 

 caviaire. There are at least eight species ; four, however, appear to yield the Isinglass 

 of commerce. The Beluga or large Sturgeon, Acipenscr Huso. The Osseter, A. 

 Guldenstadtii. The Sterlet, A. Buthemis, and the Sewraga, A. Stellatus. These 

 inhabit the Black and Caspian Sea, and the groat rivers flowing into them. See 

 CAVIAIEE ; ISIHGXASS. 



acONITiarE. C 80 W NO 14 (C 30 K 47 WO 7 ). A poisonous alkaloid constituting 

 the active principle of the Monkshood (Aconitum Napellus) and other species of Aconite. 



ACOXTXTUM. (a.K6virov.) The Greek name for the Hemlock. See CONIUM. . 



ACONITUJI is now the name of a genus of plants belonging to the l\anunculucc<e, 



