Mr. D'ARCET praises very highly the effects of these lozenges in disordered digestion, and in preventing its occurrence, as well from experiments made on his own person, as from observations on others. He believes their operation to be purely chemical, consisting in the saturation of the morbid acid of the stomach, and, therefore, not likely to be lessened by habit. Their effects are much more prompt than magnesia, either pure or in the state of carbonate. In the phosphatic diathesis, where the urine is disposed to be alkaline, it would seem that these lozenges would do harm. But, perhaps, we have this security against their use in these cases, that the stomach would not at the same time be troubled with acidity. _Annales de Chimie et de Physique, Jan._ 1826. 69. _Presence of Mercury in Samples of medicinal Prussic Acid._--Mr. REGIMBEAU, apothecary at Montpellier, has detected this impurity in some prussic acid, prepared in Paris. Its presence was first suspected, from a portion of the acid, accidentally dropped, leaving a white stain on the copper dish of a balance. It is probable, that the impure acid, spoken of, had been made by passing sulphuretted hydrogen through a solution of cyanide of mercury, according to VANQUELIN'S process; and that an insufficiency of the decomposing gas had been employed. May not this accidental impurity explain the occasional salivating effects of prussic acid. 70. _Proposed Method for preparing Protoxide of Mercury by precipitation, for Medical Employment._--Mr. THOMAS EVANS has published some observations on this subject, and justly remarks, that the blue pill, mercurial ointment, and other mercurial preparations, are not uniform compounds, but contain variable proportions of the real protoxide, and uncombined mercury. Some blue pill, which had been carefully prepared by Mr. E. by the usual process of trituration, was found to contain on analysis 20 per cent. of unoxidized mercury; and the blue mass from Apothecaries' Hall, London, furnished about the same proportion. As it is obviously a desideratum to procure preparations of protoxide of mercury of uniform strength, Mr. EVANS has been led to seek a process, by which to obtain this oxide in a pure state. After repeated experiments, he has pitched upon the following formula: Dissolve four ounces of caustic hydrate of potassa in a pound of water, and to the clear solution, decanted from any impurities, add four ounces of calomel, and shake the mixture frequently. Pour off the liquid, and wash the precipitate formed with water, and then dry it at a gentle heat.