ARSENIC. 
§ 77°-] 
597 
The process has been applied to the determination of arsenic in atoxyl, 
hexamethyl-triamino-phenyl-arsine, dicamphoryl-arsinic acid, p-tolyl- 
arsinic acid, sodium tetra-iodo-cacodylate, triamino-triphenyl-arsine, 
phenyl-triamino-triphenyl-arsine, toluene, p-sulphonyl, p-amino-phenyl- 
arsinic acid, and other organic arsenic compounds with extremely satis¬ 
factory results. 
There have been other “ dry ” methods of destroying the organic 
matter and retaining the arsenic in such compounds successfully used, 
e.g. :—Combustion of the substance mixed with soda lime in air or oxygen 
(La Caste and Michaelis, Annalen, 1880) ; simple fusion with sodium 
peroxide (Pringsheim, Amer. Chem. Journ., 1904) ; destruction of organic 
matter by nitric acid containing magnesium nitrate, the final ignition 
giving magnesium arsenate (Monthule, Ann . Chinn. Anal., 1904). 
Norton and Koch’s Method (a modified Kjeldahl).—-This method is 
equally available for arsenic in tissues, or organic derivatives. The 
objection to its use in the search for arsenic in the organs of the body is 
that it is only well adapted for testing quite small quantities up to, say, 
1 grm. ; it is essentially a Kjeldahl process :— 
From 01 to 0-2 grm. of the substance, with 10 grins, of potassic 
sulphate and a little starch, 0-2 to 0-3 grm., is placed in a Kjeldahl flask, 
20 c.c. of concentrated sulphuric acid added, and heated over a Bunsen 
flame until colourless, or only pale yellow. This takes some four to six 
hours. Any arsenic present is now in the form of arsenious acid. 
Oxidation with Permanganate. —Hupp and Lehmann (Arch. Pharm., 
1912) oxidise with permanganate. From 5 to 20 grms. of the sub¬ 
stance are mixed with 10 grms. of potassic permanganate and 10 c.c. 
of dilute sulphuric acid, on the water-bath, for some time with frequent 
agitation, then 25 c.c. of concentrated sulphuric acid added little by 
little. When effervescence ceases, the liquid is washed into a Kjeldahl 
flask with an additional 30 c.c. of concentrated sulphuric acid, cooled, 
5 grms. of NaCl added, and distilled into 100 c.c. of water and 40 grms. 
of sodium bicarbonate. The distillation is stopped when all the bicar¬ 
bonate has disappeared. The distillate is now alkalised by a further 
addition of bicarbonate and titrated with iodine. 
It is obvious in this process that, with the large quantities of chemicals 
used, such as 60 c.c. of acid, 10 grms. of permanganate, and some 50 grms. 
of salts of the alkalies, a blank experiment must be made to ascertain if 
the materials are arsenic-free. 
Distillation Processes. — Separation of arsenic by methyl alcohol (F. 
Pergatel, Monatsh., 1912).—The substance is treated with concentrated 
HC1 and methyl alcohol, and distilled ; the distillation is assisted by 
a current of dry air. The distillate is collected in water, and contains 
methyl arsenite and arsenic chloride, the latter being at once dissociated 
into hydrochloric acid and arsenious acid. The process is simple and 
