Part 7

From the above observations it is obvious that to form _pure_ quadrisulphuret of lime the atmospheric air should be excluded, as the agitation by ebullition would promote the oxidizement of the compound. I mixed 168 grains of sublimed sulphur with 96 hydrate of lime, which by previous trials I had found to consist of 70 lime including 2 or 3 grains of alumine, and 26 water; the mixture was put into a small florence flask, which was then filled with water up to the neck and loosely corked. This was immersed in a pan of water and boiled for 2 or 3 hours, the flask was continually turned round to agitate the mixture and promote the solution. After the undissolved part had subsided the clear liquor was decanted and found to be 2800 grain measures of the sp. gr. 1.056; the residuum moderately dried weighed 34 grains; it was found to contain 8 of lime and alumine, and 25 of sulphur. Hence the liquid contained 62 lime and 143 sulphur, or 2.2 lime and 5.1 sulphur per cent.; that is, after the rate of 24 lime to 56 sulphur, or 1 atom of lime to 4 of sulphur, and its weight = 80, the atom of sulphur being supposed 14. Here then we have a synthetic proof of the composition being a quadrisulphuret. Innumerable other experiments, though made with less rigid accuracy, had convinced me that the liquid is essentially the same whatever the proportions of the ingredients, and that the residuum only varies in such cases.

I have made many experiments occasionally since 1805, on the quantities of oxygen absorbed and sulphur deposited by quadrisulphuret of lime. They all concur in establishing the same conclusion; namely, that each atom of the compound takes 2 of oxygen and deposits 2 of sulphur, in its transformation from the yellow to the colourless state. For instance, 100 measures of the above 1.056 took 900 of oxygen gas = 1.22 grains, and let fall 2 grains of sulphur, besides a small portion which adhered to the bottle, which was estimated at a few tenths of a grain. The method is to put 100 measures into a graduated and well stoppered bottle filled with oxygen; to agitate briskly for half an hour, occasionally opening the stopper a little under water to admit its entrance into the place of the oxygen absorbed. Whenever the agitation has been continued for five minutes without any sensible increase in absorption, and the liquor, after standing to let the sulphur subside, appears colourless, the experiment is finished. This new combination then consists of 1 atom lime, 2 sulphur, and 2 oxygen = 66; it will be necessary to give it a name: I propose calling it sulphuretted sulphite of lime, as it is an atom of sulphur united to sulphite of lime; and the rather, as it will appear in the sequel that other neutral salts do combine occasionally with an atom of sulphur. This sulphuretted sulphite may be boiled down to the sp. gr. 1.1 before it precipitates: the liquid then contains about 12 per cent. of the salt, or 5 sulphur, 2½ oxygen, and 4½ lime. The salt precipitates from the liquid by evaporation in the form of a white powder; it burns with a feeble blue flame, and loses about 20 per cent.; the remainder is sulphite of lime. When 100 grain measures of the liquid sulphuretted sulphite (1.1) are saturated with oxymuriate of lime, they acquire 5 grains of oxygen, and then yield 12½ grains of sulphuric acid (containing 5 sulphur and 7½ oxygen), as may be found by the barytic tests. The point of saturation is known by the smell of oxymuriatic acid being given out permanently.

If however we oxidize the quadrisulphuret of lime by oxymuriate of lime, the results are somewhat different. As soon as an atom of the quadrisulphuret has received two atoms of oxygen it becomes colourless as before, but ¾ of the sulphur is thrown down instead of ½; and when more oxymuriate is added, so as to impart 3 atoms of oxygen to one of the salt, a complete sulphate of lime is formed. The point of saturation is determined by adding a small portion of muriatic acid to the liquid, which develops the oxymuriatic acid as soon as it becomes in excess. This method excels in the analysis of the alkaline and earthy sulphurets in general.

When quadrisulphuret of lime is treated with an alkaline carbonate, a reciprocal change takes place; the carbonic acid takes the lime, and the alkali the sulphur, leaving however 1 atom of sulphur with the carbonate which precipitates. Hence a sulphuretted carbonate of lime is obtained and a trisulphuret of the alkali. The sulphur burns off from the carbonate below a red heat and leaves 75 per cent. of carbonate of lime; this affords an excellent analysis of quadrisulphuret of lime as far as lime is the object. Thus 540 of the above 1.056 quadrisulphuret took 100 test carbonate of potash (1.25), and gave a precipitate of 29 grains, which burned blue and left 22 grains = 12 lime, and 10 acid; but if 540 ∶ 12 ∷ 100 ∶ 2.2, as above determined synthetically: moreover, 12 lime, 10 acid, and 7 sulphur, are as 24 lime, 20 acid, and 14 sulphur; the composition of an atom of sulphuretted carbonate of lime, which is analogous to the sulphuretted sulphite of lime, as found above.

When quadrisulphuret of lime is treated with as much sulphuric acid as is sufficient for the lime, the sulphur is in part precipitated, but it is in union with the sulphate of lime, or at least they are not separable by mechanical means. This compound is sold in the shops under the name of precipitated sulphur. It is about one half sulphate of lime, and the other half sulphur. The nitric and muriatic acids precipitate the sulphur partially from quadrisulphuret, but the sulphur assumes a viscid form and exhales sulphuretted hydrogen, and the proportion of the elements of quadrisulphuret are not easily obtained by any of these acids.

The mutual action of quadrisulphuret of lime, and the metallic salts is curious and interesting; for instance, with nitrate of lead. Let a solution of nitrate of lead, containing 97 oxide, be treated with a solution of quadrisulphuret of lime by degrees, as long as a black precipitate appears, marking the exact point of saturation; this will be found when 36 parts of lime have entered, and 84 of sulphur; the sulphuret of lead will fall, and when dried will weigh 145 parts, and contain 90 lead, and 55 sulphur; that is, 1 atom of lead, and 4 of sulphur, and is consequently a quadrisulphuret of lead. The liquid remains clear and colourless, and contains the nitric acid, lime, oxygen of the lead, and ⅓ of the sulphur; each atom of nitric acid combines with one of lime, which retains one of the 4 atoms of sulphur, forming a sulphuretted nitrate of lime, consisting of 45 acid, 24 lime, and 14 sulphur; the 7 parts of oxygen unite with 7 of sulphur to form sulphurous acid, which require 12 parts of lime to saturate them and 7 of sulphur, forming a sulphuretted sulphite of lime: hence we see that 28 parts of sulphur remain in the liquor, and the rest (56) unite with the lead. If now we add gradually more nitrate of lead, a silvery white precipitate appears, increasing till half the original quantity is added, and then the liquid is saturated. This white precipitate is sulphuretted sulphite of lead; when heated it soon grows black and loses 15 or 20 per cent., being then a protosulphuret of lead. The liquid now contains sulphuretted nitrate and simple nitrate of lime; nitrate of lead has no effect, but nitrate of mercury precipitates a black sulphuret.

Quadrisulphuret of lime saturated with oxygen, as has been observed, contains sulphuretted sulphite of lime in solution, and deposits sulphur: the liquid treated with nitrate of lead, gives as above the white, silvery sulphuretted sulphite of lead as a precipitate, and holds nitrate of lime in solution.

_Hydrosulphuret of lime._ This compound may be formed by passing sulphuretted hydrogen into lime water; the water assumes a brownish colour, but the point of saturation is not easily found, as the lime water is not neutralized so as to shew by the colour test, and water of itself absorbs above twice its volume of the gas. By means of a neutral solution of nitrate of lead it may be found that 1000 lime water in volume, require about 600 sulphuretted hydrogen, because then a mutual saturation is observed by double affinity; that is, sulphuret of lead and neutral nitrate of lime are formed; but otherwise the liquid remaining is either acid or alkaline. Hydrosulphuret of lime, as well as the other hydrosulphurets, has a peculiar bitter taste. It forms a useful reagent in regard to metals, but is apt to be spoiled by keeping, owing to the acquisition of oxygen.

2. _Sulphuret of magnesia._

I have not succeeded in endeavouring to combine sulphur and magnesia in the dry way; but a liquid sulphuret is easily formed by the action of double affinity.

Let a quantity of the liquid quadrisulphuret of lime be treated with a solution of sulphate of magnesia, so that the sulphuric acid may be sufficient for the lime; by digesting in a moderate heat, the sulphate of lime is precipitated, carrying with it one fourth of the sulphur, and a trisulphuret of magnesia remains in solution. I have not observed any remarkable feature of distinction between this sulphuret and that of lime, except as above noticed in the proportions of their compounds.

_Hydrosulphuret of magnesia._ This compound may be formed by pouring sulphuretted hydrogen water into recently precipitated magnesia; it does not differ much from that of lime. One atom of sulphuretted hydrogen (15), combines with one of magnesia (17), and the compound is soluble in water.

3. _Sulphuret of barytes._

_Protosulphuret._ The protosulphuret of barytes may be procured the same way as that of lime, by heating hydrate of barytes and sulphur till the mixture becomes red. It is very little soluble in water, and accords in other respects with the like compound of lime. It consists of 68 barytes and 14 sulphur, or 100 barytes and 20½ sulphur.

_Quadrisulphuret._ The quadrisulphuret of barytes may be formed the same way as quadrisulphuret of lime, by boiling the hydrate of barytes and sulphur together. A yellow solution of the compound is formed, not distinguishable in appearance from that of lime; and it appears to be analogous to it in most of its properties. By acquiring oxygen it becomes colourless sulphuretted sulphite of barytes, and crystalizes in needles; in this last respect it differs from that of lime. The maximum density of liquid quadrisulphuret I have not had an opportunity of ascertaining; it is 1.07 or upwards; that of the liquid sulphuretted sulphite is much less than that of lime; the crystals are found in a liquid so low as 1.004 sp. gr. They have a fine silky lustre when dry, and a yellowish colour; heated they burn with a blue flame and leave a white mass of sulphate preserving the same crystalline appearance as before, and lose about 20 per cent. of weight. Ten grains of the crystals of sulphuretted sulphite, when treated with liquid oxymuriate of lime to saturation, require 2+ grains of oxygen and yield 8 grains of sulphate of barytes, together with an excess of sulphuric acid which with muriate of barytes gives 8 grains more of sulphate. From these facts it may be concluded that the sulphuretted sulphite consists of one atom barytes, 2 sulphur, 2 oxygen, and 2 water, and that 4 more of oxygen are derived from the oxymuriatic acid to convert the sulphurous oxide into sulphuric acid. The sulphuretted sulphite of barytes seems to pass into sulphate by length of time. The weight of the atom of quadrisulphuret of barytes is 124; the compound in mass consists of 100 barytes and 82 sulphur.

_Hydrosulphuret of barytes._ This compound may be formed in the same manner as that of lime, and is found to have similar properties. The proportions for mutual saturation are, I find, as in the case of lime, 15 sulphuretted hydrogen to 68 barytes by weight, or one atom of each.

4. _Sulphurets of strontites._

The protosulphuret and quadrisulphuret of strontites may be formed in the same way as those of lime and barytes. From a few experiments made on these compounds I have not observed any remarkable feature of distinction between them and the corresponding ones of the other earths.

_Hydrosulphuret of strontites._ This compound may be formed in the same way as that of lime; the proportions to produce mutual saturation will be 1 atom of each, or 15 parts sulphuretted hydrogen, to 46 strontites by weight.

5, 6, 7, 8, _and_ 9. _Sulphurets of alumine, silex, yttria, glucine_, and _zircone_.

I made several unsuccessful attempts to combine alumine and sulphur. When alumine and sulphur mixed together are heated, the sulphur sublimes chiefly, and leaves the alumine with traces of sulphate of alumine.

In the humid way, recently precipitated and moist alumine mixed with sulphur and boiled in water, give a liquid with some traces of sulphuric acid, but no sulphuret of alumine; the sulphur and alumine both subside, and when the sulphur is either sublimed or burnt, the alumine remains much the same as at first. When a solution of alum is treated with sulphuret of lime, sulphate of lime is precipitated along with the greatest part of the sulphur in a kind of feeble union rather than mechanical mixture, it should seem; the alumine is at the same time precipitated probably in mechanical mixture; there remain in solution a little sulphuret of potash and sulphate of lime.

_Sulphuret of silex_ is not known, I apprehend, to exist. When silicated potash in solution is treated with quadrisulphuret of lime, a copious dark brown or black precipitate instantly appears; the liquid when filtered is of a pale yellow colour, and seems to contain about one half of the sulphur and potash, whilst the other half is thrown down in union with the lime and silex. This black compound is probably 1 atom of lime, 2 of sulphur, 2 of potash, and 2 of silex; it cannot therefore be accounted a sulphuret of silex.

_Sulphurets of yttria_, _glucine_, and _zircone_, are as yet, I presume, unknown.

10. _Sulphurets of potash._

Potash has a strong affinity for sulphur and unites with it in various ways and proportions.

1st. _In the dry way by heat._ When either pure potash or the carbonate (salt of tartar) is heated in a covered crucible with sulphur, a chemical union of the two principles takes place. Eight parts of dried hydrate of potash unite to six or seven of sulphur: a heat of 4 or 500° of Fahrenheit is convenient for the purpose. If the carbonate of potash be used, then 12 parts dried in a low red heat will require 8 of sulphur for their complete saturation: in this case a higher degree of heat is requisite in order to expel the carbonic acid; a low red heat seems sufficient from my trials. When the heat does not exceed 3 or 400° a partial union takes place; the carbonate of potash, without losing any acid, unites to ⅓ of the sulphur, and the rest of the sulphur remains uncombined; when intermediate degrees of heat are used, I have found the result a mixture of the pure sulphuret and the carbonated sulphuret, with more or less of sulphate of potash. A high degree of heat and exposure to the atmosphere produces a sulphate instead of a sulphuret. The sulphurets obtained this way are in fusion till poured out and cooled; they are of a _liver_ colour, and hence were formerly called _livers_ of sulphur. They are largely soluble in water, and give a brownish yellow solution.

2d. _In the humid way by solution._ Pure caustic potash in solution when boiled with sulphur dissolves it largely, 42 parts of real potash being saturated with about 56 of sulphur. If we boil a solution of carbonate of potash with sulphur, for an hour or more, a brown liquor is obtained, which consists of 60 parts carbonate of potash and 14 sulphur in chemical union.--It has already been observed that a trisulphuret of potash may be obtained by double affinity from quadrisulphuret of lime and carbonate of potash, together with sulphuretted carbonate of lime.

From what has been stated we may infer at least three varieties in the compounds of sulphur and potash, viz.

1st. _Sulphuretted carbonate of potash._ This consists of 1 atom carbonate of potash (61) with 1 atom of sulphur (14). Its analysis may be effected as follows: the quantity of carbonic acid may be found by the lime water necessary to saturate it; the potash may be known from the quantity previously entering into the mixture; and the sulphur in the same manner, or from the quantity of sulphuretted carbonate of lead that it forms.--The sulphur may also be known, from the quantity of oxygen it requires by means of oxymuriate of lime to produce saturation; this I find to take place when the oxygen is half the weight of the sulphur, or one atom to one of sulphur; it soon happens, that one atom of sulphur deprives two others of their oxygen, and sulphuric acid is formed whilst the other two atoms of sulphur join the carbonate of lime and are precipitated along with it. As it may frequently happen, that the sulphuretted carbonate is mixed with common carbonate of potash, the proportions may be found by means of nitrate of lead, which being cautiously dropped into the solution, lets fall first the brown sulphuretted carbonate of lead, and then the common white carbonate of lead.

The sulphuretted carbonate of potash absorbs oxygen and precipitates metals much the same in appearance as the other sulphurets; but essential distinctions are observable, some of which are noticed above, and others will appear in the sequel.

2 and 3. The _trisulphuret_ and _quadrisulphuret_ of potash so nearly resemble the quadrisulphuret of lime in their properties, as not to require any additional remarks.

_Hydrosulphuret of potash._ This combination, when duly proportioned, consists of 15 parts sulphuretted hydrogen, and 42 potash by weight, or one atom of each. It may be formed by directly uniting the two elements, or by decomposing hydrosulphuret of lime by carbonate of potash. Its properties agree with those of the other hydrosulphurets.

11. _Sulphurets of soda._

I have repeated most of the experiments on the sulphurization of potash with soda, and have not found anyone remarkable feature of distinction, besides those which arise from the weights of the atoms.

1. _Sulphuretted carbonate of soda_ consists of 1 atom of carbonate of soda united to 1 of sulphur; or of 47 parts of the former and 14 of the latter.

2. _Trisulphuret of soda_ consists of 1 atom soda (28) and 3 of sulphur (42).

3. _Quadrisulphuret of soda_ consists of 1 atom soda (28) and 4 atoms of sulphur (56).

_Hydrosulphuret of soda._ This compound consists of one atom of each of the elements, or 15 sulphuretted hydrogen, and 28 soda. In other respects it agrees with hydrosulphuret of potash.

12. _Sulphuret of ammonia._

The best way which I have found of procuring sulphuret of ammonia, is to treat quadrisulphuret of lime with the carbonate of ammonia as long as any precipitate takes place; the precipitate is sulphuretted carbonate of lime, 3 atoms of sulphur to 1 of carbonate of lime. The liquid is of a pale yellow, and contains ammonia and sulphur united in the ratio of 1 atom (of 6) to 1 of sulphur: it may therefore be denominated the protosulphuret of ammonia.

The carbonate of ammonia is best procured by heating the common subcarbonate of ammonia, first pulverized, in a temperature of 100° for half an hour, or exposing it for a few days to the atmosphere. What remains of the salt is almost without smell; it should consist of 19 parts acid, 6 ammonia, and 8 water nearly: the ammonia is usually however a small degree in excess.

_Hydrosulphuret of ammonia._ This compound may be formed in the dry state by combining the two gases of sulphuretted hydrogen and ammonia over mercury; it is of a white crystalline appearance, and very soluble in water, and forms a fuming liquor of a very pungent smell. It may also be obtained by passing sulphuretted hydrogen into a vessel containing liquid ammonia. I find about 110 or 120 measures of sulphuretted hydrogen require 100 of ammoniacal gas. Hence it is 1 atom of sulphuretted hydrogen (15), that unites to 1 of ammonia (6).

13. _Sulphurets of gold._

There exist at least two sulphurets of gold, the nature and proportions of which are easily ascertained; though several authors assert that no combinations of gold and sulphur are known; amongst these it is surprizing to find Proust: indeed most of the others have probably been led by his authority to adopt the opinion without examination. It is not very easy to account for his deception.

Obercampf, in the Annal. de Chimie, tom. 80. 1811, is the first author I have seen who distinctly maintains the existence of one or more sulphurets of gold, though it seems to have been admitted previously by Bucholz. The last author finds 82 gold unite to 18 sulphur, and the former 80 to 20 nearly.

_Protosulphuret of gold._ This compound is formed whenever a solution of muriate of gold is agitated with sulphuretted hydrogen gas, or with the same united to a base, as lime or alkali. A black or deep brown powder falls down by the addition of more gas, till the whole of the gold is precipitated. The oxide of gold loses one atom of oxygen, and receives one of sulphur in its place, whilst the hydrogen of the gas is carried off along with the oxygen of the oxide. The sulphuret dried and heated, burns with a blue flame, leaving the gold nearly pure. This compound consists, I find, of 81 gold and 19 sulphur per cent.; or 100 gold unite to 23 sulphur.

_Trisulphuret of gold._ This compound is obtained whenever quadrisulphuret of lime is gradually dropped into a solution of muriate of gold; it is a black powder, not quite so deep as the former. Care must be taken to saturate the excess of acid previously by lime water, to prevent any uncombined sulphur precipitating. Trisulphuret of gold being heated, burns with a blue flame, and leaves the gold nearly pure; it loses from 10 to 45 per cent. by the process. It is constituted of 1 atom gold and 3 sulphur, or 60 gold and 42 sulphur, nearly; or 100 gold combine with 70 sulphur.

From several experiments I am led to conclude that each atom of oxide of gold takes 3 of sulphur, and parts with 1 of oxygen to the remaining sulphur; thus a trisulphuret of gold is formed, and an oxide of sulphur; the liquid, being afterwards treated with oxymuriate of lime, is found to require twice the oxygen of the gold for its saturation, when a corresponding portion of sulphuric acid may be precipitated by muriate of barytes.

14. _Sulphuret of platina._

Sulphur may be combined with platina in several ways, and probably in different proportions; but the combination is not so easily and elegantly effected as with many other metals, and hence some uncertainty still remains on the subject.