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ADDITIONAL NOTES

TO

THE SECOND VOLUME.

NOTES TO ESSAY IX.

ON THE FIXED ALKALIES.

1. Nitrum.- Page 6, line 10. NITRUM or natron was without doubt known to the ancients, though we have no evidence that nitre was. In the Proverbs of Solomon, chap. xxv. ver. 20, it is said, that “ As he that taketh away a garment in cold weather, and as vinegar upon nitre, so is he that sings songs to a heavy heart;" here the word ought certainly to be nitrum or natron, for on this vinegar would occasion a violent effervescence, though not upon salt-petre or nitre. “A memoir on an extraordinary collection of salt-petre, which was made in France during the years 1794 and 1795, also on a new method of refining this salt, by C. A. Prieur," will be found in the Annales de Chimie, tome xx. page 298.

An account of a remarkable cave in Kentucky in the United States of America, called Mammoth Cave, which contains an extraordinary quantity of salt-petre, may be seen in the Archæologia Americana, pages 355-361.

2. Very corrosive.- Page 7, line 16. This alkali in its pure state is so corrosive that it is employed by the surgeons for what is called their Potential cautery. Boerhaave relates, that an unfortunate man who fell into a boiling copper of a lixivium of caustic potash, tiad all the soft parts of his body dissolved, and nothing remained but his bones.

See Dallow's edition of Boerhaave's Elements of Chemistry, quarto, vol. ii. page 43. Dreadful accidents have sometimes happened

ADDITIONAL NOTES

Τ Ο

THE SECOND VOLUME.

NOTES TO ESSAY IX.

ON THE FIXED ALKALIES.

1. Nitrum.- Page 6, line 10. NITRUM or natron was without doubt known to the ancients, though we have no evidence that nitre was. In the Proverbs of Solomon, chap. xxv. ver. 20, it is said, that “ As he that taketh away a garment in cold weather, and as vinegar upon nitre, so is he that sings songs to a heavy heart;" here the word ought certainly to be nitrum or natron, for on this vinegar would occasion à violent effervescence, though not upon salt-petre or nitre. “A memoir on an extraordinary collection of salt-petre, which was made in France during the years 1794 and 1795, also on a new method of refining this salt, by C. A. Prieur," will be found in the Annales de Chimie, tome xx. page 298.

An account of a remarkable cave in Kentucky in the United States of America, called Mammoth Cave, which contains an extraordinary quantity of salt-petre, may be seen in the Archæologia Americana, pages 355—361.

2. Very corrosive.- Page 7, line 16. This alkali in its pure state is so corrosive that it is employed by the surgeons for what is called their Potential cautery. Boerhaave relates, that an unfortunate man who fell into a boiling copper of a lixivium of caustic potash, had all the soft parts of his body dissolved, and nothing remained but his bones. See Dallow's edition of Boerhaave's Elements of Chemistry, quarto, vol. ii. page 43. Dreadful accidents have sometimes happened

froin persons having swallowed caustic alkali. The late Dr. Johnstone, an eminent physician of Worcester, when writing on this subject remarks, that "it will perhaps require 8 or 10 grains of caustic alkali to destroy texture, for a small quantity would be neutralized by the carbonic acid it meets with in the passage, or by the contents of the stomach itself."-Johnstone on mineral poisons, page 150. See also an article under the title of “ Causticity" in the Additions to Macquer's Dictionary of Chemistry, octavo, vol. ii.

3. Barilla imported.–Page 9, line 28. A gentleman who is just returned from Spain, where he has resided several months, has obtained the following information. “The best barilla usually exported to Ireland grows," he says, " in the neighbourhood of Alicant. It is gathered from the months of August to October. A considerable quantity of the finest quality is sent to Paris, of which their superior crystal glass is made. It is usually purchased in November; and a curious circumstance is connected with the bargain, viz. that though the price be fired when the barilla is received by the merchant, the latter obliges himself to make good any advance which may take place until Christmas-day; so that of course cargoes arrive at their destination, and are disposed of, before their real cost is known. When the crop promises to be scanty, it is necessary to bribe the farmers by anticipated payments. Abundance of barilla is made at Carthagena, and throughout the province of Valentia."

4. Rendered caustic.- Page 12, line 7. As it is important to those who ase large quantities of the fixed alkalies to know when a proper quantity of lime has been used to render them caustic—the following directions will probably be acceptable to many individuals. When the solution of caustic alkali is prepared, take a little of the clear liquor in a wine-glass, and breathe into it through a small glass tube, or otherwise add a few drops of a clear solution of subcarbonate of potash; for if there be a redundance of lime, the dissolved earth will absorb carbonic acid from the carbonate of potash or from the human breath, and this will render the liquor turbid. If this treatment should not occasion the liquor to become turbid, it should then be treated with a little lime-water; and if this occasions a turbidness, it shows that the liquor contains carbonated alkali, and consequently has not had a sufficient quantity of lime; whereas, if the lime be in due proportion, the lixivium will suffer no change from the addition of the above tests, nor will it effervesce with acids.

5. Caustic potash.—Page 12, line 17. Directions for preparing caustic potash in a dry state, will be found in Boerhaave's Elements of Chemistry, quarto, vol. ii. page 42. Whenever it is necessary to open a bottle of pure alkali, it should be done in a dry air, or near a fire, and then the stopper immediately returned and carefully secured by wax as at first. Directions for the preparation of pure potash and soda by means of alcohol are given by Dr. Henry in his Elements of Experimental Chemistry, vol. i. page 255. See also Davy, in the Philosophical Transactions for 1808, page 355 : and the Essay on Water, vol. ii. page 366. An account of the method which Lowitz has adopted for obtaining the alkalies of the greatest purity, in a crystallized state, will be found in Nicholson's Quarto Journal, vol. i. page

164. 6. Fern.- Page 17, line 1. A chemical friend who has had much experience in the preparation of the fixed alkalies, and who requested that I would allow him the perusal of my Essay on that subject, has sent me the following remarks on what I have said respecting the agency of Fern in milling woollen cloth; and which he attributes not to the alkali which it contains, but merely to its mechanical operation on the cloth. As I should not deal candidly with my readers if I withheld these remarks, I here give them exactly as I have received them. “I entertain strong doubts," says he, “ of the juices of fern or any other vegetable plant containing an alkali in a free state, having always considered incineration to be an essential process for the development of that salt. I have made several experiments on the kelp weed and other of the fuci, but could never perceive the least trace of free alkali in their expressed juice, although the ashes produced by burning them always gave indications of its presence. These vegetables probably contain neutral salts, (the sulphates of potash and soda for example, which undergo a decomposition in the fire, and in which their own carbon probably acts as a powerful agent."

7. Kelp.- Page 38, line 5. Jameson states, that barilla contains from 84 to 23 per cent. of pure alkali divested of water and carbonic acid, and that kelp contains from 2 to 5 per cent. From an analysis which I myself made of three parcels of barilla in the year 1801, one of which was from Alicant, another from Carthagena, and the third from Teneriffe, all of which were at that time esteemed to be the best samples in the London market; I found that 112 lbs. of

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