Class VI. in question. After being washed and dried, it explodes by percussion, but more feebly than the preceding salt. It does not explode by strong sulphuric acid. When heated on a slip of platinum, it goes off somewhat like gun-powder, producing a flash of white light. In chlorine gas it is decomposed with a feeble explosion, and a white cloud and flame are produced. 20. Fulminate of silver. This is the salt originally prepared by Howard, by the same process as that by which fulminating mercury was obtained. Brugnatelli's process is very easy. He puts into a beer glass 100 grains of dry nitrate of silver, and pours over it one ounce of alcohol, and as much smoking nitric acid. An effervescence takes place, and fulminating silver formed. Liebig's process is to dissolve 1 part of silver in 20 parts of nitric acid of the specific gravity 1·367, and to pour over the solution 26 parts of alcohol of the specific gravity 0.84. The mixture being raised to the boiling temperature, and kept in that state till a muddiness begins to appear, it is then taken from the fire, and to moderate the boiling, 26 parts of alcohol are added by small quantities at a time. Fulminating silver is deposited in small, white, opaque needles. When taken internally, it acts as a virulent poison. It does not act on litmus paper. It is anhydrous, or contains only traces of water. When exposed to the light, it becomes black, and is decomposed, carbonic acid, azotic gas, and vapour of water being given out. When heated, it explodes with great violence. It explodes also by percussion and friction, and the contact of concentrated sulphuric acid. When put into dry chlorine gas, it explodes with flame, and a loud report. 36 parts of boiling water dissolve one part of fulminate of silver, but it is again precipitated when the liquid cools. It dissolves easily and completely in liquid ammonia. We have two analyses of this salt which so far agree, that they show the salt to be a compound of an atom of acid, and an atom of oxide of silver, though they are inconsistent with each other as far as the elements of the acid are concerned. Mr. Edmund Davy found the salt composed of According to the analysis of Gay-Lussac and Liebig, the constituents are Sect. IV. I have already pointed out the difference in the constitution of fulminic acid to which these two analyses lead.† 21. Fulminate of gold. When a weak solution of chloride of gold is added to liquid fulminate of barytes, a dark precipitate slowly separates. When washed and dried on the filter, it has a chocolate brown colour, and explodes with a loud report, and a reddish flame, by heat or percussion. It is soluble in dilute muriatic acid. Nitric acid decomposes it. When the liquid from which the preceding fulminate has precipitated is evaporated after filtration, it yields small yellow crystals in six-sided prisms, which explode by heat and percussion with a reddish and yellowish flame. Whether these crystals be the same as the chocolate powder, or whether they constitute a different species, has not been ascertained.‡ 22. Fulminate of platinum. It may be obtained by adding a solution of sulphate of platinum to liquid fulminate of barytes as long as a precipitate falls. A dark brown substance gradually separates, which when washed and dried is fulminate of platinum. When heated, it is decomposed with a hissing noise; by percussion, it is decomposed, producing smoke, but scarcely any sensible noise. This substance consists chiefly of sulphate of barytes. But the liquid from which it separates when evaporated, deposites pure fulminate of platinum in minute rhombic prisms, having a yellowish brown colour, and exploding loudly by heat and percussion.§ 23. Fulminate of palladium. Nitrate of palladium being added to fulminate of barytes, a dark brown substance gradually falls, which after being washed and dried, explodes by heat with a reddish flame. This fulminate has a dark brown colour, and is tasteless and insoluble in water.|| 24. Fulminate of chromium. This compound may be formed by treating fulminate of barytes with sulphate of chromium. The filtered solution after evaporation yields minute crystals * Ann. de Chim. et de Phys. xxv. 285. † See page 232 of this volume. E. Davy, p. 48. § Ibid. p. 50. | Ibid. p. 51. Class VI. of fulminate of chromium, having a yellowish green colour. They are soluble in water, and the solution has a sweet and slightly astringent taste. They explode by percussion and heat, producing a feeble report, and a reddish flame.* SECTION V.—OF SULPHO-CYANODIDES AND HYDRO-SULPHO CYANATES. From the account of hydro-sulpho-cyanic acid, given in page 241 of this volume, it appears to have for its base a compound of 2 atoms sulphur 4 3.25 7.25 To which the name of sulpho-cyanogen has been given. This base, united to one atom hydrogen, constitutes the hydro-sulpho-cyanic acid, or the sulphuretted chyazic acid of Porrett. Most of the saline compounds, into which this acid enters, would appear to be compounds of sulpho-cyanogen and the respective bases; but as the subject has not yet been sufficiently cleared up, I have prefixed both names to this section; though I am of opinion that most of the salts (except the first) are in fact sulpho-cyanodides. 1. Hydro-sulpho-cyanate of ammonia. Liquid ammonia dissolves very little hydro-sulpho-cyanic acid. When the solu tion is evaporated the whole of the ammonia is disengaged.† This salt does not crystallize, but is soluble in alcohol.‡ 2. Sulpho-cyanodide of potassium. This salt may be ob tained by mixing together equal weights of flowers of sulphur and common prussiate of potash, previously deprived of its water and reduced to the state of a fine powder, and fusing the mixture over a spirit-lamp at a temperature a little below ignition. When the fused mass has become cold dissolve it in water and drop into the solution caustic potash till all the oxide of iron is thrown down, then filter and evaporate to dryness. The dry salt thus obtained (if too much potash has not been added) is sulpho-cyanodide of potassium. It crystallizes in long colourless channeled prisms, and needles terminated by four-sided prisms. Its taste is biting, and similar to that of radishes, but it leaves a saline and cooling impression in the mouth. It is poisonous, and acts as a narcotic. When heated * E. Davy, p. 14. + Wöhler. + Porrett. it melts into a transparent liquid, which assumes a crystalline Sect. V. texture on cooling. If air be excluded, it may be ignited without decomposition; but in an open vessel it is gradually converted into sulphate of potash. According to Porret, it is deliquescent, and I have found it so in my laboratory. It is readily soluble in alcohol. Its constituents, according to the analysis of Berzelius, are 1 atom sulpho-cyanogen 3. Sulpho-cyanodide of sodium. rhomboids. It is deliquescent, and 7.25 5 12.25 This salt crystallizes in 4. Sulpho-cyanodide of barium. A deliquescent salt, crystallizing in long slender prisms of a brilliant white colour. This salt, according to the analysis of Mr. Porrett, is com Hydro-sulpho-cyanic acid posed of Barytes Doubtless the true constituents are 1 atom sulpho-cyanogen 1 atom barium 30.1 69.9 100.0 7.25 8.5 15.75 5. Sulpho-cyanodide of strontium. A deliquescent salt, crystallizing in long slender prisms in groups, radiating like zeolite. 6. Sulpho-cyanodide of calcium. A deliquescent salt, soluble in alcohol, from which it may be obtained in a mass of needle-form crystals. 7. Sulpho-cyanodide of magnesium. A deliquescent, incrystallizable salt. When dried it has a micaceous appearance. 8. Sulpho-cyanodide of aluminum. It crystallizes in octahedrons, and does not deliquesce. 9. Hydro-sulpho-cyanate of iron. This salt may be obtained by dissolving iron in an aqueous solution of hydro-sulphocyanic acid. It has a light bluish green colour, a sweet and astringent taste, and reddens litmus paper. The salt is very soluble in water. The solution becomes red when exposed to * Porrett. Class VI. the air, or when mixed with chlorine, nitrous acid, &c. and at the same time deposites a yellow ochre, consisting of a subsalt. 10. Hydro-sulpho-cyanated peroxide of iron. A salt of a beautiful crimson colour, deliquescent, and only obtainable in a solid form by exposure to an atmosphere artificially dried. When in a solid state it appears black by reflected light. 11. Sulpho-cyanodide of manganese. A colourless salt, very soluble in water, but almost insoluble in absolute alcohol. 12. Sulpho-cyanodide of nickel. Very soluble in water.† 13. Sulpho-cyanodide of cobalt. It may be obtained by mixing an aqueous solution of sulphate of cobalt with the aleoholic solution from which sulpho-cyanodide of potassium has been precipitated. The sulpho-cyanodide shoots into blue coloured prisms, which, when exposed to the air, become first violet and finally of a rose red colour. By the addition of water, they become nearly colourless; but alcohol restores the blue colour again.‡ 14. Sulpho-cyanodide of zinc. 15. Sulpho-cyanodide of lead. drons, and deliquesces in a moist Very soluble in water.§ It crystallizes in rhombohe atmosphere.[] 16. Sulpho-cyanodide of tin. Very soluble in water.¶ 1 atom hydro-sulpho-cyanic acid copper 7.375 9 16 375 18. Sulpho-cyanodide of copper. This salt may be formed by mixing together solutions of sulpho-cyanodide of soda and sulphate of copper. It is then in the state of a bright peagreen liquid, to which, if any deoxidizing substance, as sulphurous acid, an alkaline sulphite, or the salts of protoxide of * Porrett. † Idem. Grotthuss. § Porrett. ¶ Idem. |