Ure's Dictionary of Chemistry. 34-1 



of water. Oil of vitriol, for instance, in this view, instead of consisting of 

 81.5 real acid, and 18.5 water in 100 parts, may be regarded as a compound 

 of 32.6 sulphur + 65.2 oxygen + 2.2 hydrogen. When it is saturated with 

 an alkaline base, and exposed to heat, the hydrogen unites to its equivalent 

 quantity of oxygen, to form water which eraporates, and the remaining 

 oxygen and the sulphur combine with the base. But when the acid is made 

 to act on a metal, the oxygen partly unites to it, and hydrogen alone 

 escapes." 



" Carbonic acid he (Dr. Murray) admits to be destitute of hydrogen; 

 yet its saturating power is very conspicuous in neutralizing dry lime. 

 Now, oxalic acid, by the last analysis of Berzelius, contains no hydrogen. 

 It differs from the carbonic only in the proportion of its two constituents. 

 And oxalic acid is appealed to by Dr. Murray as a proof of the superior 

 acidity bestowed by hydrogen. 



" On what grounds he decides carbonic to be a feebler acid than oxalic, 

 it is difficult to see. By BerthoUet's test of acidity, the former is more ener- 

 gettc than the latter, in the proportion of 100 to about 58 ; for these numbers 

 are inversely as the quantity of each requisite to saturate a given base. 

 If he be inclined to reject this rule, and appeal to the decomposition of the 

 carbonates by oxalic acid, as a criterion of relative acid power, let us 

 adduce his own commentary on the statical affinities of Berthollet, where 

 he ascribes such changes not to a superior attraction in the decomposing 

 substance, but to the elastic tendency of that which is evolved. Ammonia 

 separates magnesia from its muriatic solution at common temperatures ; at 

 the boiling heat of water, magnesia separates ammonia. Carbonate of 

 ammonia, at temperatures under 230°, precipitates carbonate of lime from 

 the muriate ; at iiigher temperatures, the inverse decomposition takes 

 place with the same ingredients. If the oxalic be a more energetic acid 

 than the carbonic, or rank higher in the scale of acidity, then, on adding to 

 a given weight of liquid muriate of lime, a mixture of oxalate and car- 

 bonate of ammonia, each in equivalent quantity to the calcareous salt, oxa- 

 late of lime ought alone to be separated. It will be found, on the con- 

 trary, by the test of acetic acid, Uiat as much carbonate of lime will pre- 

 cipitate as is sufficient to unsettle these speculations." 



Under Acid (Arsenious) we find a very copious account of 

 its poisonous operation on the living body, as also of its tests 

 and antidotes. 



" We may here remark, however, that the most rlegant mode of using 

 all these precipitation reagents is upon a plane of glass, a mode practised 

 by Dr. W ollaslon in general chemical research, to an extent, and with a 

 success, which would be incredible in other hands than his. Concentrate by 

 heat in a capsule the suspected poisonous solution, having previously fil- 

 tered it if necessary. Incleed, if it be very much disguised with animal or 

 vegetable matters, it is better first of all to evaporate to dryness, and by a 

 few drops of nitric acid to dissipate the organic products. The clear liquid 

 being now placed in the middle of the bit of glass, lines are to be drawn 

 out from it in different directions. To one of these a particle of weak ara- 

 moniacal water being applied, the weak nitrate of silver may then be 

 brushed over it with a hair pencil. By placing the glass in different lights, 

 either over white paper or obliquely before the eye, the slightest change 

 of tint will be perceived. The ammoniaco-acetate should be applied to 

 another filament of the drop, deut-acetate of iron to a third, weak auimo- ■ 

 niaco-acetate of cobalt to a fourth, sulphuretted water to a filth, lime-water 

 to a sixth, a drop of violet syrup to a seventh, and the two galvanic wires 

 at the opposite edges of the whole. Thus vnth one single drop of sola- 

 tion many exact experiments may be made." 



A plane of white paper answers extremely well for the same 

 microscopic tests, as recommended by Dr. Paris. 



The proportional or atomic weight of alum, or prime equi- 

 valent, as Dr. Urc calls it, he deduces from Sir H. Davy's ex- 

 periments, to be 32, and not 21.36, as assigned by Berzelius, 



Vol. Xi. 2 A 



