After this a third specimen was received from Huelgoeth; it was very small, but as rich as the foregoing, and in it there were distinguishable, besides granular cubic crystals of chloride of silver, other grains of an olive-green color, which had exactly the same appearance as the bromide had. Plateros and the following experiments proved the presence of the substance.
Five grammes of the pulverized mineral were boiled in a solution of oxalic acid, until the oxide of iron was perfectly dissolved: the residue weighed about a gramme, and it evidently contained a mixture of canary-yellow and white grains. It was digested in hot solution of ammonia until all the yellow powder disappeared; it required a large quantity of the alkali for this purpose, which would not have been the case to dissolve pure chloride. The solution was gradually saturated with nitric acid, and it was observed that the successive deposits formed had an evident yellow tint, but gradually diminishing in intensity, except the last, which were white. The yellow deposits were collected and examined in the following manner:—A portion was treated with chlorine and æther; the æther became of a yellow color. Another portion was dissolved in ammonia, hydrosulphate of ammonia was added to the solution, and the black precipitate formed was separated, and was found to be pure sulphuret of silver. The liquor was concentrated by exposure to the air, and filtered to separate the sulphur which was deposited; a little potash was then added, and it was evaporated to dryness; acetic acid was added to saturate the excess of potash, and it was again dried.
To determine whether the saline residue contained a bromide, a small portion of it was treated in a tube with pure nitric acid, and a yellow liquid was immediately obtained. Another portion was mixed with peroxide of manganese, and the mixture was placed in a glass tube; a few drops of concentrated sulphuric acid were added, and when gently heated, red vapors were immediately disengaged, and alter some lime there were deposited on the sides of the tube small drops of a red liquid. The existence of bromine was therefore evident, and it was proved that the bromide was unmixed with iodide. Bromide of silver appears to be rare at Huelgoeth; but it may be readily distinguished from the chloride by its greenish or canary-yellow color, which is characteristic of it. It is remarkable that it occurs with the chloride in the same specimens, but without there being an intimate mixture of the two substances.
The Daguerreian Journal.
NEW YORK, MARCH 1, 1851.
HILLOTYPE.
Since the announcement of the Hillotype, in the last number of the Daguerreian Journal, quite an excitement has prevailed, both in the Daguerreotype and scientific world. The great question has fairly been solved and "natural colors" can be produced and rendered indelible upon the metallic plate. America can safely say she has presented to the world one of the most invaluable discoveries that has ever been imprinted upon the pages of history.