24 PBOCEEDINGS OP THE AMERICAN ACADEMY 



lY. 



THE QUANTITATIVE DETERMINATION OF ARSENIC, BY 



THE BERZELIUS-MARSH PROCESS, ESPECIALLY 



AS APPLIED TO THE ANALYSIS OF WALL 



PAPERS AND FABRICS. 



By Charles R. Sangeb. 



Presented May 13, 1891. 



The original method of Marsh* was published in 1836, and in the 

 following year Berzelius f proposed the modification which couples 

 his name with that of Marsh. It seems to have escaped notice, at 

 least I can find no mention of the fact, that Berzelius also suggested 

 the quantitative application of the method. He proposed to place 

 some pieces of copper in the reduction tube, and, after weighing 

 tube and copper, to heat and pass the arsenical gas through. The 

 copper would further the reduction of the arseuiuretted hydrogen, 

 and thus the arsenic might be collected and weighed. Wohler,! in 

 1861, proposes essentially the same method, but heats the tube in 

 two places, at the copper which he uses in the form of a spiral, two 

 inches long, and also just behind the copper, so that whatever gas 

 escapes decomposition by the first heating may be decomposed by 

 the copper. The first practical application of this method seems to 

 have been made by GautierJ in 1876, in the estimation of arsenic 

 contained m tissues. He omits the copper spiral, but heats the re- 

 duction tube by a layer of charcoal 20 to 25 cm. in length. To de- 

 termine the arsenic deposited, he weighs the tube, dissolves out the 

 mirror by nitric acid, and, after drying, weighs again. Croramydis,|| 

 a year later, follows Gautier's method in a similar research. 



Chittenden and Donaldson, H in 1881, investigated this method 

 with very satisfactory results, and suggested the improvements which 



* Edin. Philos. Journ., XXI. 229. 



t Berzelius, Jahresb., XVII. 191. J Mineral-analyse, p. 232. 



§ Ann. d'llygiene publ. et de Me'd. legale, 1876, p. 136; also Bull, de la Soc. 

 Chim., [2.] XXIV. 250. 



II Bull, de la Soc. Chim., [2] XXV. .348. 



H American Chemical Journal, Vol. II. No. 4 ; Chem. News, XLIII. 21 ; 

 Moniteur Scient. de Paris, 1881, p. 227. 



