ally as required, so that the boiling may not be checked by a large addition of water at any time-this pan may be heated by a flue from the furnace, by which means a considerable expenditure of fuel will be saved.

As a considerable quantity of earthy matter &c. will soon begin to fall to the bottom of the boiler, and form a hand cake, which is very injurious to the metal, a small pan ought to be placed in the centre of the solution, raised two inches from the bottom of the boiler, in which this earthy matter will collect, this pan is to be suspended by means of iron chains, connected by a rope to a pulley above, so that it can be raised up from time to time, and its contents emptied into a box or basket placed at the edge of the boiler, to allow the water to drain back. It is essential that the solution should boil at an equal steady temperature, increasing or diminishing the fire as may be necessary, and the skum ought to be carefully and frequently removed.

When all the extra water has been added, the pan is to be withdrawn from the bottom of the boiler-The common salt will then begin to fall, and must be removed with a scoop ladle from the bottom, and placed, in a basket as beforementioned to drain.

It is proper at this period to decrease the fire which delays the operation, but the results are thereby obtained with more regularity. When the common salt falls to the bottom in abundance, the solution is approaching the proper degree of concentration, which may be easily ascertained by taking out a small portion of the liquid and placing it in a vessel to crystallize. &c.

When it is judged proper to stop the operation the fire is to be decreased, and the solution left to repose, till the common salt ceases to fall, or about five hours, during which time the solution ought to be kept steadily at the temperature of about 88 Centigrade thermometer or 190 of Farenhiet when it may be drawn off from the surface into crystallizing pans, taking every care to leave un disturbed, the salt or sediment at the bottom. It will require three days to complete the crystallization in winter, and longer in summer, and during hot weather fewer crystals will be obtained.

The mother water is then to be removed from the pans, and they are to be put up to drain, two and two, inclining towards each other in a channel.

In the manufactories of the Administration the crystallization is determined, by a much more easy and expeditious operation, the water is run off, into a long and large reservoir, lined with sheet lead or copper, the interior dimensions of which is about 12 feet

long, by 7 feet broad at the surface, the bottom is formed with a double slope of four inches towards the centre, one from the sides, the other longitudinally, so that the depth at one end is 16 inches and at the other end 20 inches.

The water is kept constantly in motion by means of wooden rakes to assist in cooling it, and the crystals as they form are raked to one end of the reservoir heaping them up to drain, and removing the most elevated parts, as they whiten perceptibly, to be carried to troughs or baskets and left to drain. In thus removing successively the small crystals as they form, the agitation, of the water with rakes must be continued incessantly to prevent the Saltpetre from forming in large cakes.-When the water has fallen in temperature to within 4 degrees of the place, or in about six hours all the Salt petre will have been obtained, and the water will remain collected in the centre and towards one end of the reservoir from whence it is easily removed.

On the treatment of the water of crystallization.

This water will be left fully saturated with nitre and common salt, with a portion of earthy nitrates which may not be decomposed and ought to be again treated with a small proportion of potass, or pass. ed over ashes, and then evaporated-or this water may be mixed with other Saltpetre water, before the latter has been treated with potass. If it is evaporated separately, the water which again remains may be abandoned or sold.

In France the earthy substances removed from the bottom of the boiler, is washed to recover the nitre remaining in it, the skum is boiled up in good water for the same purpose, and the refuse salt, which also contains a considerable proportion of Saltpetre is treated as follows.

*

A boiler is to be filled three parts full of water and brought to boil; pure common salt is then thrown in till the water is fully saturated, which will be known by some of the salt falling to the bottom, the excess is removed with a scoop. Have in readiness some

baskets filled with the refuse salt, one of these baskets, is to be immerged in the boiling solution, which cannot dissolve any more common salt, and can only act upon the nitre contained in it, in a short time, this basket may be withdrawn, and another put in, and so on till the water in the boiler is fully saturated with nitrate of potass, when it may be drawn off to crystallize. The baskets are put into the boiler by means of ropes, and a pulley fixed to a Crane. I have made trial of this system of treating the refuse salt, and I find that it will amply re-pay the cost, by the quantity of Saltpetre recovered.

VII.-Assay of Saltpetre according to the principle established by M. M. Botté et Riffault in France.

This process consists in using a dissoluent of salts of earthy bases and of muriate of Soda which at the same time will not act upon the nitrate of potasse, and in leaving it undisturbed would shew the exact quantity of pure nitre contained in any given quantity of grough Saltpetre; this dissoluent is water fully saturated with pure nitre; if care is taken to obtain the saturated solution at the time of using it, in a fully saturated state.

The following is the method to be pursued.

Method of preparing the saturated

solution.

Take about two or three pounds of pure nitre pounded and sifted, and throw it by degrees into a copper vessel tinned inside about 12 inches deep, and 5 inches diameter pouring in at the same time, good water heated to 126 degrees of Fahrenhiet, to be well stirred, and left for three or four hours or during the night, there ought always to be a portion of pure nitre not dissolved at the bottom, and the solution ought never to be used without stirring it well up from the bottom, and allowing it only one minute to settle, each time of using it.*

The Saltpetre received is to be collected in a heap, and well mixed, and a quantity taken from different parts of the mass, from which a sample; or any number of samples of 100 drams avoirdupois each is to be taken, the saltpetre taken for assay must be well bruised in a mortar.

One of these samples of 100 drams is to be placed in a glass vessel (a common finger glass or cooler is well adapted for this operation) and half a pint of the saturated solution poured upon it, and constantly stirred with a glass rod for 15 minutes, then allow it to settle for an instant, and pour off the surface water into a paper filter placed in a funnel over any vessel, this paper filter is necessary in order to retain any nitrate of potasse which may escape by carelessness in pouring off the surface water.

The Saltpetre in the glass vessel is then to be washed a second time with a quarter of a pint of the saturated solution, and stirred with a glass rod constantly for 15 minutes, allowed to settle and

* In France where this mode of assay is pursued, an instrument called an Aréometre, with a thermometer are used to ascertain, that the solution is fully saturated up to the temperature of the place before using it, but the assay may be conducted with great accuracy without these instruments if the rules here laid down are strictly observed.

the surface water poured off as before, draining off the water to the utmost, with care and attention, in pressing the nitre remaining in the vessel with a tea spoon.

The nitre remaining in the glass vessel is then to be spread upon a treble fold of filtering paper placed upon a box containing chalk or ashes or any absorbent matter, carefully removing every particle of nitre from the glass vessel; the box is to be placed in a dry place for 24 hours, the time necessary for the paper &c. to imbibe great part of the moisture-the nitre must then be carefully removed from the paper with a spoon and a knife or spatula and placed in the same glass vessel in which it was washed to be placed on a bed of sand over a gentle fire, and the salt constantly stirred with a glass rod, till the salt no longer adheres to the rod or to the vessel, when it will have fallen to a fine dry powder.

It only remains to ascertain the exact loss in quantity by weighing the nitre recovered, and to the number of drams found wanting, add one per cent for insoluble matter, such as sand or earth, and the amount will be the quantity of impurity contained in the sample of 100 drams, and of course in the whole mass of grough saltpetre received of which it was a part.

Should the result of the assay shew a loss of weight of 60 per cent. it will be necessary to wash the sample a third time with half a pint of the saturated solution, which would be more than suffici ent to dissolve the whole that remains of the sample should it prove to be altogether nothing but common salt.

Thus if 100 drams of saltpetre is taken for assay the following form may be observed.

Taken for assay, saltpetre...

Drams.

100

Recovered after washing and drying.

79

Impurities....

21

* Add one per cent. for insoluble matter such as gravel, sand, &c....

1

22

*The quantity of insoluble matter remaining in the sample, after the assay has been completed will seldom exceed one per cent, but if necessary it can be ascertained by dissolving what remains of the sample in boiling water and passing the solution through filtering paper, the insoluble matter will remain upon the paper, and can easily be collected, dried and weighed.

VIII.-At a General Meeting of the Madras Literary Society and Auxiliary of the Royal Asiatic Society, held at the College on Thursday the 30th January 1834.

Present.

The Honorable Sir R. PALMER, President in the Chair.

The Hon. W. OLIVER, ESQ.

Revd. Mr. SPRING,
Captain ROWLANDSON.
Æ. R. MCDONELL, ESQ.
W. LAVIE, Esq.

R. COLE, Esq.

Lieut. Col. NAPIER,
Dr. BENZA,

Major HODGES,

J. A. R. STEVENSON, ESQ. and
J. C. MORRIS, Esq. Secretary.

The Meeting having been opened by the Honorable the President, the Secretary laid before them a statement of the Funds of the Society in both its branches.

The meeting then proceeded to elect new members for the Committee of Management, and for the Committee of Papers, of the Asiatic Department for the ensuing year.

On the proposition of the Honorable the President, seconded by the Honorable Mr. Oliver, the following gentlemen, were unanimously elected members for the Committee of Management.

Lieut. Col. Garrard,

J. Annesley, Esq.
Revd. Mr. Spring,

Proposed by the Honorable the President, and seconded by Lieut. Col. Napier, that the following gentlemen be requested to become members of the Committee of Papers.

Dr. Benza,

J. G. Malcolmson, Esq.

H. S. Fleming, Esq. M. D.
R. Cole, Esq.

On the proposition of the Secretary, the thanks of the meeting were unanimously voted to Dr. Benza, and Lieut. Col. Cullen, for their valuable services in classing, arranging, and naming the large collection of mineral and geological specimens, in the Society's

museum.

The following donations having been made to the Society, since the last annual general meeting, the thanks of the Society were unanimously voted to the donors.

Notitia Linguae Sinicæ...

Lieut. Newbold,