OF ARTS AND SCIENCES. 25 



Parts. 

 Copper sulphate, 6 



Arsenic trioxide, 2 



Sodium carbonate, Na^CO3l0H2O, 8 



Dissolve the soda and arsenic in ten parts of water, and the copper 

 sulphate in forty parts of water ; filter botli solutions if necessary. Mix 

 while boiling, boil for a few minutes, and then allow to stand until 

 next day ; pour off the supernatant licjuid, fill up the vessel with hot 

 water ; repeat this operation about three times, then filter, and dry at 

 about 100° C. 



In analyzing these salts, the water was determined by ignition in a 

 current of oxygen. The water being collected and weighed in a 

 chloride of calcium tube. The arsenic was determined in various 

 ways, but it was found that the conversion into arsenic pentoxide and 

 trituration with uranium solution gave the most satisfactory results. 

 The copper was determined with the battery. 



The separation of copper and arsenic was made either by boiling 

 with a slight excess of potassa with previous oxidation by nitric acid 

 or bromine, or by adding potassa, and then passing hydrogen sulphide 

 through the solution until the copper was completely precipitated. 



My thanks are due to my assistant, E. R. Hills, for the able manner 

 in which he has aided me by making many analyses of these salts, — an 

 undertaking that can be appreciated only by those who have tried 

 working with copper and arsenic in combination. 



Since the above paper was finished, I have succeeded in obtaining 

 two samples of copper arsenite as found in commerce. The first of 

 these resembled closely that analyzed in Analysis No. XII. in color, 

 and on examination it was found to contain carbon dioxide and sul- 

 phur trioxide ; the other resembled Analysis No. XVIII., and, like it, 

 contained a trace of sulphate. 



Boston, June 1st. 



