bituminous matter, but have little iron, lime, or other substances which might injure the quality of the alum, or interfere with its profitable production. These are known by the names of blaze, cannel, slate, coal, metal, fire-clay, stone, &c., &c., any of them constituted as just mentioned, and which break up into shivers or lamina, on being for some time exposed to atmospheric influence, either before or after calcination, is fit for my purpose.

This property, in connection with their aluminous constitution, is what peculiarly adapts them for my process, the laminated struction giving an immense surface to the action of the acid in the process of digestion.

But though I prefer these materials, as naturally fitted for my mode of treatment, to be afterwards described, (and which, so far as I am aware, have not, with the exception of fire-clay, been hitherto used for the manufacture of alum,) other materials which have been used for that purpose by other processes, as common or potter's clay, may be artificially rendered available for it, by breaking or cutting into small fragments.

I prepare these shales for digestion by calcining them in the following manner.

I form on the ground a number of air-channels, one or two feet apart; each of these channels is constructed by laying two parallel lines of common bricks, each line at about four inches distance from the other, and then laying other bricks across, forming a channel about four inches square. The bricks are laid loosely, so as to allow the air to pass freely upwards; on these channels I lay burning coals, and over them some of the more bituminous shales, broken into small pieces, adding, when the combustion has commenced, other pieces of less bituminous sorts. These are put on gradually as required, care being taken to keep up the ignition of the mass, and yet not to permit the heat to rise above a low red. A higher heat than this is apt to glaze or partially flux the materials, and render the alumina less soluble in the acid.

Shales destitute of bitumen, or prepared clays, may be calcined in the same way by mixing with them small coals or saw dust. The heaps, in either case, may be made of any convenient length and breadth, but had better not exceed four to five feet in height. They will burn out, and be cool enough for use in eight or ten days from commencing.

I take the materials thus calcined, and introduce them, for the purpose of digestion, into vessels similarly constructed to those used in my copperas process, viz., vessels of lead, or of wood, iron, or stone, &c., lined with lead. I however, prefer large square vessels lined with lead, and to heat by means of steam.

These are fitted with the materials to within two or three inches of the top, and diluted sulphuric acid run on till it is covered.

The strength of the diluted acid should be specific gravity 12 to 1.25. This strength is not selected for its superior action on the shales, but on the same principle as is stated in the description of my copperas process, viz., in order that a solution of alumina may be produced which, on the addition of the necessary salts of potash or ammonia, will be of the proper strength for crystallization of alum, without having recourse to evaporation.

When the diluted acid is introduced, I apply heat till the temperature is about 200 degrees Fahrenheit, at which it should be kept for twenty to twenty-four hours; at the expiration of this time, the neutralization is nearly completed, and the liquor is run off into proper coolers, as described in my copperas process.

A new charge of diluted acid, or as the working progresses, the mother liquors and sulphuric acid, of same specific gravity as before, is then poured on the materials, the heat is applied, and in from twenty to twenty-four hours it is again ready for running.

This process is repeated six or seven times, when the material is generally so exhausted of alumina as to be unworthy of further attention; it is then washed by covering with water, which is run off and saved, then thrown out, and a new charge introduced, to be treated in the same

manner.

In this way I make my solution of sulphate of alumina, to be used in the manufacture of alum, or if the sulphate of alumina is to be manufactured into concentrated alum, or solid sulphate of alumina, then special care is to be taken that the solutions are quite neutral, such solutions are obtained by selecting the first and second runs from the material, digested with water and acid only, and may be purified and finished in the way usually adopted by manufacturers of that article.

And this alum I immediately produce when the sulphate

of alumina is run off into the coolers, by adding, either in a state of solution, or while the liquor is still hot, dissolving in it directly the equivalent quantity, found by trial, of a sample of sulphate, or other salts of ammonia, or salts of potash, but I prefer ammonia. The alum is now deposited in the coolers, as the liquor cools, and is taken out and finished for the market in the usual way.

The mother liquors, after depositing the alum, are pumped up into the digesting vessel, to be used with more sulphuric acid as already mentioned.

In regard to my improvements in the manufacture of alum, I do not claim the use of fire-clay, or other aluminous materials, save the said bituminous shales, as applied to the manufacture of alum by other processes, nor the use of potash or ammonia, or other compounds, for the production of alum from sulphate of alumina, otherwise produced. What I claim is,

Firstly, the sole use of the various kinds of shale or shist, with the exception of those varieties known as alum shist, which contain both bituminous and aluminous matter to furnish alumina for the manufacture of alum.

Secondly, the mode of manufacturing sulphate of alumina from such shists or shales, and also from fire-clay, shist, and such other aluminous substances as are suitable from their shivery or laminated texture for my process, or such as may be artificially so fitted, by digesting them by the aid of heat, with repeated quantities of diluted sulphuric acid, or mother liquors and sulphuric acid.

Thirdly, the production, by these means, of solutions of sulphate of alumina, of the proper strength for crystallization, of alum on the addition of salts of ammonia or potash, without having recourse to evaporation.

Fourthly, the production of alum, by adding potash or ammonia, or any salt of potash or ammonia, to the solution of sulphate of alumina thus produced,-In witness, &c.

Enrolled May 27, 1846.

PETER SPENCE.

No. 1.-VOL. VIII.

Ꭰ

Specification of the Patent granted to ARTHUR SMITH, for Improvements in the Manufacture of Soda Ash.Sealed October 23, 1845.

To all to whom these presents shall come, &c., &c.— My invention of improvements in the manufacture of soda ash consists in the substitution of the vat-waste or residuum of the lixiviation of the black ash, in place of using fresh calcareous matter, for making the mixture of sulphate of soda, carbonaceous matter, and chalk or lime, which is subjected to decomposition in the reverberatory furnace.

The manner of carrying out this invention is to mix the vat-waste, or residuum mass, obtained from preceding operations of the soda manufacture in required proportions, with ground coal black, or charcoal and salt-cake, or sulphate of soda, and to expose the mixture on the hearth of a reverberatory furnace to a strong heat, with due stirring and turning over, till the mixture becomes fully fused and decomposed. The said vat-waste is preferable for the purpose, after it has lain sometime exposed in a heap to the atmospheric influences, whereby it becomes deprived, to a considerable degree, of its sulphureous impregnation.

The proportion of vat-waste to be used for a certain weight of sulphate of soda and slack depends upon the proportion of calcareous matter in the waste, and can therefore be regulated for each particular heap only by trial or experiment. When it is relatively poor in calcareous matter, it must be used in a proportionately larger quantity.

Having now described my invention, and the manner of carrying the same into effect, I wish it to be understood, that I claim, under the above, in part-recited letters patent,

The substitution of the said vat-waste in place of fresh calcareous matter, either in whole or only in part, in mixing the materials for the reverberatory furnace operations of the soda manufacture.-In witness, &c.

Enrolled April 23, 1846.

ARTHUR SMITH.

Specification of the Patent granted to EDEN THOMAS JONES, of Bristol, Manufacturing Chemist, for Improvements in the Apparatus used in the Concentration of Sulphuric Acid.-Sealed November 27, 1845.

To all to whom these presents shall come, &c., &c.In the common process of concentrating sulphuric acid, when glass vessels are used for that purpose, considerable inconvenience and uncertainty have been experienced from the frequent breaking of the glass vessels in the operation, the consequent loss of the acid, to the great annoyance of the neighbourhood, and from the necessity of maintaining a high degree of temperature in the laboratory for the purpose of defending the glass vessels from all drafts or currents of cold air, which invariably proves so destructive to the glass vessels, when considerably heated. To remedy these inconveniences attending the old process, I apply a vessel, which I call a protector, of sheet-iron or tin, or of any other suitable material, not liable to be injured by the heat of the process, the form of which is immaterial; it may be cylindrical or square, or of any other figure, provided it completely envelops the glass retort or vessel when at work.

These covers or protectors are for the purpose of defending the glass vessels from injury, especially from currents of cold air. The covers or protectors are made from four or five inches of greater diameter and height than the glass retorts, and encloses a volume or atmosphere of hot air all round the retort during the operation.

By this means the process is shortened, a considerable saving in fuel and labour is effected, and the glass vessels last longer.

I would remark, that I do not confine myself to the details here given, so long as the glass retorts used in this manufacture are protected when at work by covering them, so as to prevent the prejudicial effects arising from the contact of cold air; and I wish it to be understood that what I claim as my invention is,

The protecting vessels of glass or glass retorts used in the concentration of sulphuric acid, for the purpose of defending them from the injurious effects of cold air.-In witness, &c.

Enrolled May 27, 1846.

EDEN THOMAS JONES.