solemn day,”—and twice asked me to read the Bible to，
"Now for one word of advice to the tyro: Remember that you are working with prussic acid; therefore, never conduct the process in a room, the fumes being quite as poisonous as the solution of the acid itself; moreover, have always a bottle of ammonia or chlorine by your side, that should you have chanced to inhale more than is pleasant, it will be instantly at hand to counteract any bad effects. It is stated by Pereira, that a little sulphuric acid or hydroferrocyanic acid passes to the outer vessel, but probably the amount would be of no consequence for electro-metallurgy, otherwise, it might be as well to use a Woulfe's apparatus, and discard the salt formed in the first vessel. To the large manufacturer it may be worth considering whether some other metallo-cyanuret, formed in a similar manner to the ferrocyanuret, might not be more advantageously employed, because the residue of the process last described contains a large quantity of cyanogen which the acid is unable to set free.
"There are other modes of procuring prussic acid, besides the one which has been so tediously described; but these are found to be more expensive. The only one which I shall now notice is the process by which it is obtained from bicyanide of mercury. The bicyanide of mercury itself is formed when peroxide of mercury is digested with Prussian blue, the peroxide of mercury abstracting the whole of the cyanogen from the blue, and leaving the oxides of iron at the bottom of the vessel. The solution may be evaporated to dryness, and one part of the salt dissolved in six of water; one part of muriatic acid, sp. gr. 1.15, is then added, and the solution distilled, when the whole of the hydrocyanic acid passes over, and by being conducted into a solution of potassa, as in the former process, forms cyanuret of potassium. This process, though easier than the first described, is rather given as a resource under peculiar circumstances than as one to be adopted by the large manufacturer. The expense is the only objection, but in a small quantity this cannot be a consideration.
"In giving this very rough outline of the general mode of forming salts, the minutiae necessary for chemical work have altogether been avoided, and those parts alone are entered upon which are more immediately necessary for the electro metallurgist to know and practice for himself. This will account for the long description of the cyanuret of potassium, while the preparation of the equally important and even more used acids, the sulphuric, muriatic, etc., commonly found in commerce, are altogether neglected.
"In using solutions of cyanide of potassium, the workman should not immerse his arms into them, otherwise it occasionally happens that the solution produces very troublesome eruptions over the skin."
Hyposulphite of Soda.--This salt forms one of the important chemicals for the Daguerreotype operator. Its application to this art is of an interesting nature. It is used to dissolve the sensitive salt of silver which remains unchanged during the exposure in the camera. It has the property of readily dissolving the chloride, bromide and iodide of silver. It should be pure and free from sulphuret of sodium; should this last be present, it will cause brown spots of sulphurated silver upon the Daguerreotype impression. This annoyance is a great source of complaint from many operators, and ever will be, so long as it is prepared by men who have no reputation to lose, and whose eyes are blinded by the "Almighty Dollar."
A good article may be prepared as follows:
"Mix one pound of finely pulverized carbonate of soda with ten ounces of flowers of sulphur, and heat the mixture slowly in a porcelain dish till the sulphur melts. Stir the fused mass, so as to expose all its parts freely to the atmosphere, whereby it passes from the state of a sulphuret, by the absorption of atmospheric oxygen, into that of a sulphite, with the phenomenon of very slight incandescence. Dissolve in water, filter the solution, and boil it immediately along with flowers of sulphur. The filtered concentrated saline liquid will afford, on cooling, a large quantity of pure and beautiful crystals of hyposulphite of soda."
Hyposulphite of Gold.--This compound salt is by a few considered preferable to the chloride of gold, but our experience has induced us to use the latter, believing we are enabled to produce a more brilliant and warm-toned impression with it. When the hyposulphite of gold is used in gilding, it requires less heat and a longer application, as there is some danger of producing a glossy scum over some parts of the surface of the plate. I prepare this salt as follows:
article title：solemn day,”—and twice asked me to read the Bible to
Address of this article：http://dgkwy.iwfinews.com/html/986a198605.html
This article is published by the partner and does not representHuchaolongxiang.comPosition, reprint, contact the author and indicate the source：Huchaolongxiang.com
current location： nature > >solemn day,”—and twice asked me to read the Bible to
TAGS:
