CHE AMEBIOAB A.OADEMT. 



'or Bands. A standard Bolution ia made by dissolving 



::1 of re 3ablimed areenious oxide in a Bmal] quantity of Bodio 



hydroxide 6 oio, acidifying with Bulphuric arid and making 



„j, • || recently boiled water. Of this solution (1 LOco. 



with freshly boiled water, giving a Bolution (II) 

 which contains 0.01 mg. ur LO micromilligrams (mmg.) of areenious 

 oxide per oubio centimeter. In testing the delicacy of the method we 

 prepared solutions containing 1 mmg. (Ill) and 0.1 mn 

 per cubic centimeter. 

 Prom definite portions of solution II, measured from a burette, a 

 dor bands is made by the above procedure, using a fresh 

 charge of tine and acid for each portion. Figure 1 (Plate 1) Bhows in 

 the actual size of the set of bands made by us, corresponding to 

 the following amounts of areenious oxide in micromilligrams: 2, 5, 

 15, 20, 25, 30, 35, 10, 50, 60, 70. The color in the Lowest values 

 lemon yellow, shading from this to an orange yellow and through 

 age yellow to reddish brown in the higher values. 



/' . --, rvation and D> vebpm nt qfth Color Bands. The rapid fading 

 the stains has been a serious obstacle to the use of the Gutzeit re- 

 ion for a quantitative method, and it became very soon evident to 

 us that Borne means of preserving the color bands must be found before 

 the me hod could be considered an entirely practical one. It was 

 (lie chief factors in the change of color were light and mois- 

 ture, the latter being by far the more important. Concerning the 

 shanism of the reactions, either for the formation of the color or for 

 imposition with water, the work of those who have investigated 

 the reactions was not sufficient to guide us. 



The early work <>l Rose 9 on the action of arsine on excess of mer- 

 curic chloride in solution showed that a yellowish brown precipil 

 formed having the empirical formula AsHg 8 Cl«. This was con- 

 1 by Rose to be made up of mercurous chloride and a compound 

 v and arsenic, to which the formula AsjHgg might be given. 

 ■ n and Bergeret 10 consider the compound bo be a mixture 

 uic and mercurous chloride 



.■hi, 11 apparently without knowledge of Rose's work, passed 



through an aqueous solution of mercuric chloride. The Liquid 



b 8 Light yellow, then red, and there was precipitated a 



sol rat yellow, but with excess of gas a dark red. "of the 



• Pogg. Annal., 51. 428 (1840). 

 « Comptea Rendues, 79. 118 (1874). 

 " L'OroBi,13, 289 iI-'jO). 



