in preparing bromide of potassium, the U. S. Pharmacopoeia first mixes iron filings and bromine together with water so as to form the bromide of iron in solution, and then adds a solution of carbonate of potassa so long as it produces a precipitate. The iron of the bromide is protoxidized by the oxygen of the potassa, and then combines with the carbonic acid of the carbonate to form the carbonate of iron which is precipitated; while the liberated bromine and potassium, uniting, remain in solution as bromide of potassium, which is obtained separate by filtration, evaporation, and crystallization.

* Dr. J. Lawrence Smith, of Louisville, proposes the following formula for a suitable solution in cases of hospital gangrene. " Dissolve 160 grains of bromide of potassium in two fluidounces of water, add one troyounce of bromine, and, stirring diligently, pour in sufficient water to make the solution measure four fluidounces." (U. S. Dispensatory, 12th ed., p. 174.) if requisite, this may be diluted with water to whatever extent may be deemed advisable. {Note to the third edition.)


Thus obtained, bromide of potassium is a colourless solid, having the crystalline form of cubes or quadrangular prisms. it is inodorous, and has a saline taste analogous to that of common salt, but more pungent, and somewhat peculiar. it is anhydrous and permanent in the air, and when heated first decrepitates and then melts, without undergoing decomposition. it is very soluble in cold, and still more so in hot water, and is slightly soluble in alcohol.- The salt may be known to be a bromide by mixing its solution with chlorine water, and shaking the mixture with ether. The chlorine takes the potassium, and the separated bromine is dissolved by the ether, which rises to the surface of a red colour. The potassium is recognized by forming a white crystalline precipitate of bitartrate of potassa when tartaric acid is added to its solution. The presence of iodide of potassium, which is a not unfre-quent impurity, is detected by the change of colour of starched white paper to a faint blue or violet, when introduced into a solution of the salt, to which a few drops of chlorine water have been added. The chlorine liberates the iodine which changes the colour of the starch.

Effects on the System

Not a little difference of opinion has existed on this point. While originally considered, and still considered by some as an alterative and deobstruent, inferior only to the analogous preparation of iodine, it is believed by others to be wholly destitute of these powers, and, indeed, rather to be opposite in its effects to iodine, than to be analogous with it. Some experimenters have found it in moderate doses to exercise powerful influences on the system, enfeebling and even partially paralyzing the fauces, and acting as a decided antaphrodisiac; and, in larger doses, or too long continued, to produce peculiar poisonous effects. Others, on the contrary, have taken it largely, and continued it for a long time without injurious result, or indeed any very striking result of any kind.* The truth probably is that, without being a

* As there is insufficient space in the text, it may be desirable for the reader to have presented, in the form of a note, an account of some of the experiments referred to, in order that he may judge of the correctness of the conclusions to which I have been led. M. Puche gave to syphilitic patients what were at the time considered as enormous doses of bromide of potassium. Beginning with doses of 2, 4, and 6 grammes (about ^ss, ^i, and jiss) dissolved in a mucilaginous potion, he gradually increased them to 10, 15, and 20 grammes (about sijss, giv, and ^v), commencing from the eighth or tenth day of the treatment. Headache was one of the first results, which, without increasing in violence, was soon accompanied with a kind of hebetude, a species of drunkenness resembling that frequently met with in typhoid fevers, and disorders of sight and hearing. There was evidently a weakness of the memory and understanding; and with this feeling of intoxication was commonly joined a tendency to drowsiness, and sometimes even a true somnolence; but rarely delirium. There was also a remarkable tendency to stumbling, and often the powerful alterative and deobstruent, it is not entirely destitute of those properties, and may take a place in this respect with the iodide of potassium, though greatly inferior in power. its characteristic property, howpatients could scarcely keep themselves on their legs. in connection with these symptoms, the sensibility was blunted, so that the patient might be pinched, pricked, or burnt without being fully conscious of what was done; but this anaesthetic effect was not constant, and could be obtained only after a certain number of days, and from larger doses of the medicine than it would be prudent to exhibit.

According to the same experimenter, from the second evening of the treatment there is sometimes produced a complete insensibility of the pharynx and velum pendulum, so that one may titillate the uvula, and touch the tonsils or the back part of the pharynx, without provoking the slightest movement of deglutition. The same insensibility exists in the conjunctiva. The genito-urinary organs are similarly affected, nocturnal erections cease, and the patients fall into a condition of impotence, which sometimes outlasts the use of the medicine several days. M. Puche was witness of a case in which incontinence of urine came on during the use of the bromide, and ceased as soon as it was suspended.

Very different from bromine itself, the bromide does not appear to exercise an irritant action on the alimentary canal; though it occasions a slight local excitation, as shown by its effects on the mucous membrane of the mouth, when the dose is not sufficiently restrained. But none of this excitation is produced on the system; on the contrary, a considerable reduction of the circulation, similar to that caused by digitalis, is not unfrequently experienced by patients under the influence of large doses of the medicine.