114 PROCEEDINGS OP THE AMERICAN ACADEMY. 



mine whether a volatile arsenical compound was liberated. He 

 ridiculed the ideas of Riedel and v. Basedow, and considered that the 

 arsenic could not even leave the walls as dust. His experiments were 

 as follows. Four grams Neuwiecler green were mixed with paste and 

 lime taken from a damp part of a ground floor wall, and placed in a 

 two-necked WoulfF bottle. After 19 days he observed no odor of garlic, 

 nor indeed could he observe any in the five years that elapsed before 

 his results were published, during which time the mixture remained 

 in the bottle. Five hundred litres of air were then drawn through 

 the bottle for 21 days, the air first passing through alcoholic potassic 

 hydroxide. The solution was then neutralized by hydrochloric acid, 

 and, "on treatment with arsenic free zinc, gave no arsenic." We have 

 here no idea of the delicacy or accuracy of the test used. 



Next, a solution of argentic nitrate was substituted for the potassic 

 hydroxide and air drawn through for fifteen days. No change was 

 observed in the silver solution, but it was not tested for arsenic. He 

 then passed the air from the bottle for five days through a hard glass 

 tube heated in two places and obtained no mirror of arsenic. He 

 next thinks that the arsenic compound, if formed, should be mixed with 

 hydrogen before absorption, and so places a hydrogen generator in front 

 of the bottle. The hydrogen generated from 133 grams of zinc, after 

 filtration by cotton wool, was passed through the bottle, then through 

 a solution of alcoholic potassic hydroxide, then silver solution, and 

 finally through the hot tube. He found no trace of arsenic in the 

 solutions or in the tube. The test is not given. During the whole 

 time there was no evidence of mould in the bottle. 



Krahmer states that he had lived for eight years in a dry and airy 

 room, the walls of which had received during that time three coats of 

 Neuwieder green, probably five pounds at a time. He never felt any 

 trouble from its presence. He repeatedly examined the dust for 

 color, but never found any. To decide the question as to arsenic in the 

 dust, he drew fifty litres of the air of the room through nitric acid, and 

 added to it the dust that had fallen on a piece of paper during that 

 time. The acid was then neutralized with sodic carbonate, evapo- 

 rated, and the sodic nitrate melted. The residue was dissolved in 

 water, filtered, and the filtrate tested with zinc and hydrochloric acid. 

 He found no arsenic, which is hardly to be wondered at in the 

 presence of so much nitric and nitrous acids. He could not find 

 copper in the filtrate, but this was probably lost by ignition and 

 filtration. 



If Krahmer's experiments had been otherwise properly conducted, 



