‘She said yesterday, “I have been dreaming.” I observed,，
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:
Dissolve one part chloride of gold and four parts hyposulphite of soda in equal quantities of distilled water: pour the gold into the hyposulphite solution, in the same manner as in mixing the gilding solution; let it stand until it becomes limpid; filter and evaporate to dryness. Re-dissolve and add a few grains of burnt alum.
After standing a few hours, filter and evaporate again. If not sufficiently pure, repeat the crystallization until it is so. For gilding, dissolve in water and use in the same manner as the common gilding solution.
N.B.--The four following mixtures were employed in Neipce's process in his earliest experiments:
Aqueous Solution of Bichloride of Mercury.--Eight grains of bichloride of mercury in 10,000 grains of distilled water.
article title：‘She said yesterday, “I have been dreaming.” I observed,
Address of this article：http://dgkwy.iwfinews.com/html/972d198619.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 > >‘She said yesterday, “I have been dreaming.” I observed,
TAGS:
