63 O POISONS : THEIR EFFECTS AND DETECTION. [§§ 799 - 803 . 
cent.—is a yellowish or reddish-brown powder, non-volatile even at a white heat ; 
insoluble in water, but dissolving in acids. Ignited on charcoal, it is reduced to 
metal, which volatilises, and is then deposited again as oxide, giving to the charcoal 
a distinct coat of an orange-yellow colour in very thin layers ; in thicker layers, brown. 
§ 799. Cadmium Sulphide, CdS = 144—Cd, 77-7 per cent. ; S, 22-3 per cent.— 
known as a mineral termed Greenockite. When prepared in the wet way, it is a 
lemon-yellow powder, which cannot be ignited in hydrogen without loss, and is 
insoluble in water, dilute acids, alkalies, alkaline sulphides, sulphate of soda, and 
^cyanide of potassium. The solution must not contain too much hydrochloric acid, 
for the sulphide is readily soluble with separation of sulphur in concentrated hydro¬ 
chloric acid. It may be dried in the ordinary way at 100 ° without suffering any 
decomposition. 
§ 800. Medicinal Preparations. —The iodide of Cadmium (Cdl 2 ) occurs in white, 
flat, micaceous crystals, melting at about 215*5° (419-9° F.), and at a dull-red heat 
giving off violet vapour. In solution, the salt gives the reactions of iodine and 
cadmium. The ointment of iodide of cadmium (Unguentum cadmii iodidi) contains 
the iodide in the proportion of 62 grains to the ounce, or 14 per cent. 
Cadmium Sulphate is official in the Belgian, Portuguese, and French pharmacopoeias. 
§ 801. Cadmium in the Arts, etc. —Cadmium is used in various alloys. The 
sulphide is found as a colouring ingredient in certain toilet soaps, and it is much 
valued by artists as a pigment. The iodide of cadmium is employed in photography, 
and an amalgam of metallic cadmium to some extent in dentistry. 
§ 802. Fatal Dose Of Cadmium. —Although no deaths from the use of cadmium 
appear to have as yet occurred, its use in photography, etc., may lead to accidents. 
There can be no question about the poisonous action of cadmium, for Marme , 1 in 
his experiments on it with animals, observed giddiness, vomiting, syncope, difficulty 
in respiration, loss of consciousness, and cramps. The amount necessary to destroy 
life can only be gathered from the experiments on animals. A strong hound died 
after the injection of -03 grin. (-462 grain) subcutaneously of a salt of cadmium ; 
rabbits are poisoned if from 19-4 to 38*8 mgrms. (-3 to *6 grain) are introduced into 
the stomach. A watery solution of *5 grm. (7-5 grains) of the bromide administered 
to a pigeon caused instant death, without convulsion ; the same dose of the chloride 
killed a second pigeon in six minutes ; *25 grm. (3*85 grains) of sulphide of cadmium 
administered to a pigeon excited vomiting, and, after two hours, diarrhoea—it died 
in eight days. Another pigeon died from a similar dose in fourteen days, and 
cadmium, on analysis, was separated from the liver. From the above cases it would 
seem probable that 4 grms. (61-7 grains) would be a dangerous dose of a soluble salt 
of cadmium for an adult, and that in a case of chronic poisoning it would most 
probably be found in the liver. 
§ 803. Separation and Detection of Cadmium. —If cadmium be in solution, and 
the solution is not too acid, on the addition of SH 2 there is precipitated a yellow 
sulphide, which is distinguished from antimony and arsenical sulphides by its in¬ 
solubility in ammonia and alkaline sulphides. Should all three sulphides be on the 
filter (an occurrence which will seldom, perhaps never, happen), the sulphide of arsenic 
can be dissolved out by ammonia, the antimony by sulphide of sodium, leaving the 
sulphide of cadmium as the residue . 2 
The further tests of the sulphide are :— 
1 . It dissolves in dilute nitric acid to a colourless fluid, with separation of sulphur. 
2. The solution, filtered and freed from excess of nitric acid by evaporation, gives 
with a solution of ammonic carbonate a white precipitate of carbonate of cadmium 
insoluble in excess. This distinguishes it from zinc, which gives a similar white 
precipitate, but is soluble in the excess of the precipitant. 
3. The carbonate thus obtained, heated on platinum foil, is changed into the 
brown-red non-volatile oxide. 
4. The oxide behaves on charcoal as already detailed. 
5. A metallic portion can be obtained by melting the oxide with cyanide of 
1 Zeitschr. f. rationelle Med., xxix. 1, 1867. 
2 It is unnecessary to state that absence of sulphur is presupposed. 
