On mentioning these results, some time since, to Prof. Jeffries Wyman, he recalled an instance, similar to those which have been mentioned, that had occurred a short time before in his own dissecting room. The arm of a subject which had been thoroughly injected with a solution of arsenic acid, having been inadvertently thrown aside and left unnoticed for several days was found completely riddled and alive with maggots. This matter is one of some importance to chemists occupied with judicial investigations, who must not infer that a fly-blown organ can contain no arsenic; and is especially interesting from the fact that several authors have urged that the attention of experts should be particularly directed to the behavior of flies. which may alight on any matter suspected of containing poison; if they die almost immediately arsenic is probably present and must be specially sought for. One case at least is on record (vid. Galtier, Traitè de Toxicologie, Paris, 1855, 1, 406) where the experts having searched in vain for laudanum which was supposed to have produced death, were led to look for arsenic, which they found, from having observed that the flies which fed upon the suspected organs soon perished. But the subject is also, as it seems to me, worthy the attention of this society, as affording another indication of the great dif ferences which exist between animals in their several conditions of metamorphosis* and of the caution with which all experiments upon the action of remedies or poisons on animals of any one species should be received when brought forward as indications of what that action will be upon other animals. * I cannot refrain, moreover, from calling attention to its obvious bearing upon the important practical question of the destruction of insects injurious to vegetation, &c.; for it is highly probable that the larvae of many other insects besides flies are less susceptible to the action of poisons than the perfect insect. Camphor, for example, is esteemed a preventive of the common clothes-moth, and its vapor is doubtless unpleasant to, if not absolutely destructive of, that insect when in its butterfly state; but, as is well known, while it remains a worm it can feed with impunity upon woolen stuffs, no matter how thickly they may be strewn with camphor. In like manner the larvae of Dermestes and Anthreni, as proved by the experiments of Dr. Cabot (Proc. Bost. Soc. of Nat. Hist., vii, 5), can consume bird-skins which have been soaked in strong solutions of corrosive sublimate or in a saturated hot solution of arsenious acid, although they will not touch specimens which have been dipped in an alcoholic solution of strychnine. SECOND SERIES, VOL. XXVIII, No. 83.-SEPT., 1859. 22 ART. XIX. On some Reactions of the Salts of Lime and Magnesia, and on the Formation of Gypsums and Magnesian Rocks; by T. STERRY HUNT, F.R.S., of the Geol. Survey of Canada.* THE importance, in a geological point of view, of gypsum and of the carbonates of lime and magnesia in the forms of limestone, dolomite and magnesite, has led me to make a series of researches, whose results serve to explain many things hitherto obscure in the history of these substances. I propose in the present paper to describe, in the first place, certain chemical reactions of the salts of lime and magnesia; and, secondly, to consider the principal facts in the history of gypsums, and magnesian rocks, and the theory of their formation, I. On the action of solutions of bicarbonate of soda on salts of lime and magnesia. 1. In studying some years since the geological relations of alkaline mineral waters I found that by the action of a solution of carbonate of soda, a partial separation of the salts of lime from magnesia could be effected. Subsequent experiments, made with dilute solutions of bicarbonate of soda, have led me to the following results. If to a solution containing besides common salt the chlorids of calcium and magnesium in the proportion of one equivalent of each, we add a solution of bicarbonate of soda in water saturated with carbonic acid, there separates a gelatinous precipitate, which very soon becomes crystalline, Collected and washed after a few hours, it is found to consist of carbonate of lime with but a small proportion of carbonate of magnesia, which in three successive precipitations from the same saline liquid, was found to equal 2-20, 200, and 1.23 per cent. The proportion of separated carbonate of magnesia diminished as the magnesian salts predominated in the solution, which now gave no further precipitate with bicarbonate of soda, but yielded by evaporation to dryness, a granular residue of hydrated carbonate of magnesia, with very little lime. In this way, a litre of the solution gave 4:19 grams of carbonate of magnesia, (MgO, CO2) and only 0.14 grm. of carbonate of lime, while the soluble portion still retained in the form of chlorid, 1.176 grms, of magnesia, but no lime. * The experiments detailed in the first section of this paper, as well as some in the second, have appeared in the Report of the Geol, Survey of Canada for 1857; the others of this section, together with those of the third, are from the forthcoming Report for 1858. See also this Journal, [2] xxvi, 110, and the Canadian Journal for May, 1859, p. 184, Many of the original observations in the fourth section already been published in the Reports of the Survey, but are now for the first time brought together, 2. A portion of the saline solution from which about one-third of the lime had been separated as above by bicarbonate of soda, gave by thirty minutes ebullition, a precipitate which for a litre equalled 0'666 grm. of carbonate of lime and 0.173 of carbonate of magnesia. Another portion of the same solution when evaporated to dryness at 120° F., gave 0.805 of carbonate of lime, but no magnesia. 3. If in the preceding experiments we employ a somewhat dilute solution of bicarbonate of soda there is no immediate precipitation of carbonate of lime. A solution was prepared with one litre of water, 29-2 grms. of sea-salt, 13.8 of chlorid of calcium, 50 7 of hydrated chlorid of magnesium, and 100 grms. of hydrated sulphate of soda, the three chlorids being in the proportion of two equivalents of the first and third to one of chlorid of calcium. In another litre of water were dissolved 42.0 grms. (equal to two equivalents) of bicarbonate of soda, and the liquid was then saturated with carbonic acid gas. Of this solution, 500 cubic centimeters would have been required to decompose the whole of the chlorid of calcium in the first, and 200 c. c. of it were gradually added to this with stirring, but without producing any visible effect. A further portion of 100 c. c. caused a slight turbidness, which was soon replaced by a crystalline precipitate, adhering to the sides of the vessel, and gradually increasing in amount. After a repose of forty hours at 68° F., the precipitate was collected and analyzed. It weighed 4.3 grms., and was carbonate of lime, with 3.8 p. c. of carbonate of magnesia. 4. The saline liquid, augmented by the washings of the precipitate, now measured 1:400 c. c.; of this one-half was mingled with 100 c. c. of the alkaline solution, being the quantity required for the decomposition of the remaining lime salt. No immediate change was apparent, but at the end of twenty-four hours there had separated a crystalline precipitate, weighing 2.288 grms., and consisting of carbonate of lime with only 2.6 p. c. of carbonate of magnesia. 5. The reason of this separation of lime from magnesia in the above experiments is evident, when we consider that carbonate of magnesia at ordinary temperatures decomposes the soluble salts of lime. Thus, according to Mitscherlich, magnesite or dolomite slowly transforms a solution of gypsum into one of sulphate of magnesia, carbonate of lime being formed at the same time. I have observed a similar reaction between dolomite and a solution of chlorid of calcium, especially at about 125° F. De Senarmont, and after him Bineau, found that solutions of bicarbonate of magnesia decompose chlorid of calcium in the cold, or at temperatures below 212° F. with precipitation of nearly pure carbonate of line, although the assertion of the latter, that sul phate of lime is decomposed by the same agent, is, as I shall ART. XIX. On some Reactions of the Salts of Lime and Magnesia, and on the Formation of Gypsums and Magnesian Rocks; by T. STERRY HUNT, F.R.S., of the Geol. Survey of Canada.* THE importance, in a geological point of view, of gypsum and of the carbonates of lime and magnesia in the forms of limestone, dolomite and magnesite, has led me to make a series of researches, whose results serve to explain many things hitherto obscure in the history of these substances. I propose in the present paper to describe, in the first place, certain chemical reactions of the salts of lime and magnesia; and, secondly, to consider the principal facts in the history of gypsums, and magnesian rocks, and the theory of their formation, I. On the action of solutions of bicarbonate of soda on salts of lime and magnesia. 1. In studying some years since the geological relations of alkaline mineral waters I found that by the action of a solution of carbonate of soda, a partial separation of the salts of lime from magnesia could be effected. Subsequent experiments, made with dilute solutions of bicarbonate of soda, have led me to the following results. If to a solution containing besides common salt the chlorids of calcium and magnesium in the proportion of one equivalent of each, we add a solution of bicarbonate of soda in water saturated with carbonic acid, there separates a gelatinous precipitate, which very soon becomes crystalline, Collected and washed after a few hours, it is found to consist of carbonate of lime with but a small proportion of carbonate of magnesia, which in three successive precipitations from the same saline liquid, was found to equal 2-20, 200, and 1.23 per cent. The proportion of separated carbonate of magnesia diminished as the magnesian salts predominated in the solution, which now gave no further precipitate with bicarbonate of soda, but yielded by evaporation to dryness, a granular residue of hydrated carbonate of magnesia, with very little lime. In this way, a litre of the solution gave 4:19 grams of carbonate of magnesia, (MgO, CO2) and only 0.14 grm, of carbonate of lime, while the soluble portion still retained in the form of chlorid, 1.176 grms, of magnesia, but no lime. * The experiments detailed in the first section of this paper, as well as some in the second, have appeared in the Report of the Geol, Survey of Canada for 1857; the others of this section, together with those of the third, are from the forthcoming Report for 1858. See also this Journal, [2] xxvi, 110, and the Canadian Journal for May, 1859, p. 184, Many of the original observations in the fourth section already been published in the Reports of the Survey, but are now for the first time brought together. 2. A portion of the saline solution from which about one-third of the lime had been separated as above by bicarbonate of soda, gave by thirty minutes ebullition, a precipitate which for a litre equalled 0.666 grm. of carbonate of lime and 0.173 of carbonate of magnesia. Another portion of the same solution when evaporated to dryness at 120° F., gave 0.805 of carbonate of lime, but no magnesia. 3. If in the preceding experiments we employ a somewhat dilute solution of bicarbonate of soda there is no immediate precipitation of carbonate of lime. A solution was prepared with one litre of water, 29-2 grms. of sea-salt, 13-8 of chlorid of calcium, 50-7 of hydrated chlorid of magnesium, and 100 grms. of hydrated sulphate of soda, the three chlorids being in the proportion of two equivalents of the first and third to one of chlorid of calcium. In another litre of water were dissolved 42.0 grms. (equal to two equivalents) of bicarbonate of soda, and the liquid was then saturated with carbonic acid gas. Of this solution, 500 cubic centimeters would have been required to decompose the whole of the chlorid of calcium in the first, and 200 c. c. of it were gradually added to this with stirring, but without producing any visible effect. A further portion of 100 c. c. caused a slight turbidness, which was soon replaced by a crystalline precipitate, adhering to the sides of the vessel, and gradually increasing in amount. After a repose of forty hours at 68° F., the precipitate was collected and analyzed. It weighed 4:3 grms., and was carbonate of lime, with 3.3 p. c. of carbonate of magnesia. No 4. The saline liquid, augmented by the washings of the preci pitate, now measured 1400 c. c.; of this one-half was mingled with 100 c. c. of the alkaline solution, being the quantity required for the decomposition of the remaining lime salt. immediate change was apparent, but at the end of twenty-four hours there had separated a crystalline precipitate, weighing 2-288 grms., and consisting of carbonate of lime with only 2.6 p. c. of carbonate of magnesia. 5. The reason of this separation of lime from magnesia in the above experiments is evident, when we consider that carbonate of magnesia at ordinary temperatures decomposes the soluble salts of lime. Thus, according to Mitscherlich, magnesite or dolomite slowly transforms a solution of gypsum into one of sulphate of magnesia, carbonate of lime being formed at the same time. I have observed a similar reaction between dolomite and a solution of chlorid of calcium, especially at about 125° F. De Senarmont, and after him Bineau, found that solutions of bicarbonate of magnesia decompose chlorid of calcium in the cold, or at temperatures below 212° F. with precipitation of nearly pure carbonate of line, although the assertion of the latter, that sul phate of lime is decomposed by the same agent, is, as I shall |