Page:EB1911 - Volume 21.djvu/524

Substance.		Observer.	Date.
Platinum.
Chloride in ether		Gehieri	1804
Chloride with lime		Herschel	1840
Iodide		Herschel	1840
Bromide	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	Hunt	1844
Cyanide
Double chloride platinum and potassium		Dobereiner	1828
Mercury.
Oxide (mercurous)		Gay-Lussac and Thénard	1811
Oxide		Davy	1812
Oxide (mercuric)		Davy	1797
Oxide (more accurate observations)	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Abidguard	1797
		Harup not till	1801
Chloride (mercurous)		K. Neumann previous to	1739
Chloride (mercuric)		Boullay	1803
Chloride with oxalic acid		Bergmann	1776
Sulphate		Myer	1764
Oxlate (mercuric)		Bergman	1776
Oxlate (mercurous)		Harff	1836
Sulphate and ammonia (mercurous)		Fourcroy	1791
Acetete (mercurous)		Garot	1826
Bromide (mercuric)		Lowig	1826
Iodide (mercurous)	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Torosewicz	1836
		Artus	1836
Iodide (mercuric)		Field	1836
Citrate (mercuric)		Harf	1836
Tartrate and potassium (mercurous)		Carbonell and Bravo	1831
Carbonate (mercuric)		Davy	1812
Nitrate		Herschel	1840
Sulphide (mercuric)		Viruvius	1 B.C.
Iron.
Sulphate (ferrous)		Chastaing	1877
Chloride (ferric) and alchol		Bestuscheff	1725
Chloride and ether		Klaproth	1725
Oxalate (ferric)		Dobereiner	1831
Ferrocyanide of potassium		Henrich	1808
Sulphocyanide		Grotthus	1818
Prussian blue		Scopoli	1783
Ferric citrate with ammonium		Herschel	1840
Ferric tartrate		Herschel	1840
Chromate		Hunt	1844
Copper.
Chloride (cupric dissolved in ether)		Gehlen	1804
Oxalate with sodium		A. Vogel	1813
Chromate	$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right\}\,}$	Hunt	1844
Chromate with ammonium
Carbonate
Iodide
Sulphate
Chloride (cuprous)		A. Vogel	1859
Copper plates (iodized)	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Kratoch	1841
		Talbot	1841
Manganese.
Sulphate		Brandenburg	1815
Oxalate		Suckow	1813
Potassium permanganate		Frommberg	1824
Peroxide and cyanide of potassium		Hunt	1844
Chloride		Hunt	1844
Lead.
Oxide		Davy	1802
Iodide	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	Schonbein	1850
Sulphite
Peroxide		Gay-Lussac	1811
Red lead and cyanide of potassium		Hunt	1844
Acetate		Hunt	1844
Nickel.
Nitrate	$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \ \end{matrix}}\right\}\,}$	Hunt	1844
Nitrate with ferro-prussiates
Iodide
Tin.
Purple of cassius		Uncertain
Various Substances.
Cobalt salts		Hunt	1844
Arsenic sulphide (realgar)		Sage	1803
Antimony Sulphide		Suckow	1832
Bismuth salts	$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \ \end{matrix}}\right\}\,}$	Hunt	1844
Cadmium salts
Rhodium salts
Vanadic salts		Roscoe	1874
Iriduim ammonium chloride		Dobereiner	1831
Potassium bichromate		Mungo Ponton	1838
Potassium with iodide of starch		Becquerel	1840
Metallic chromates		Hunt	1843
Chlorine and hydrogen		Gay-Lussac and Thénard	1809
Chlorine (tithonized)		Draper	1842
Chlorine and ether		Calhours	1810
Chlorine in water		Bertollet	1785
Chlorine and ethylene		Gay-Lussac and Thénard	1809
Chlorine and canon-monoxide		Davy	1812
Chlorine and Hydrocyanic acid		Henry	1821
Bromide and hydrogen		Balard	1832
Iodine and ethylene		Faraday	1821
Cyanogen, solution of		Pelouze and Richardson	1837
Various other Methyl compounds		Cahours	1846
Hydrocyanic acid		Totosewicz	1836
Hypochlorites (calcium and potassium)		Dobereiner	1813
Uranium chloride and ether		Gehlen	1804
Molybdenite of potassium and tin salts		Jager	1800
Crystallization and slats under influence of light	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Cahours	1846
		Chapptal	1788
		Dize	1789
Phosphorous (in hydrogen, nitrogen &c.)		Brockmann	1800
Phosphuretted hydrogen		A. Volel	1812
Natric acid		Scheele	1777
Hog’s fat		Vogle	1806
Palm oil		Fier	1832
Asphalt		Niepce	1814
Resins (mastic, sandarac, gamboge, ammoniacum, &c.)		Senebier	1782
Guaiacum		Hagemann	1782
Bitumens all decomposed, all residues of essential oils		Daguerre	1839
Coloured extracts from flowers		Senebier	1782
Similar colouring matters spread upon paper		Herschel	1842
Yellow wax bleached		Pliny	1st cent. A.D.
Eudoxia macrembolitissa (purple dye)			10th cent.
Other purple dyes	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Cole	1684
		Réaumur	1711
Oils generally		Senebier	1782
Nitric ether		Senebier	1782
Nioctine		Henry & Boutron-Charlard	1836
Santonine		Merk	1888

Effect of Hydrogen Peroxide on Sensitive Plates.—Dr W. J. Russell made a series of experiments on the effect of exposure of sensitive plates to the action of vapours and gases for long periods. It has long been known that contact of plates with such substances as wood caused a sensitive surface to so “fog” on development. By a somewhat exhaustive series of experiments, Russell showed that the probable cause of this fog is hydrogen peroxide, since substances which favoured its formation produced the same effect. This is somewhat remarkable, as this same substance will completely destroy the effect that light has had on a sensitive plate; indeed, it affords one way of destroying a light image on a sensitive collodion plate. The experiment of Russell give a warning to store exposed plates for brief periods. It appears that negatives wrapped in paraffin paper are secure from this danger.

The Application of Photography to Quantitative Measures.—In order to employ photography for the measurement of light it was necessary that some means should be devised by which the opacity of the deposit produced on the development of a plate could be determined. It is believed that in 1874 the first attempt was made by Sir W. Abney to do this. In the Phil. Mag. he showed how density could be measured by means of an instrument, the diaphanometer, he had devised, in which transparent