MHOS OP T 1 1 1 : AHEBXCAH ACADEMY. 



A5AL1 PICA! Data. 



tthod, as far as it concerns the determination of arsenic in a 

 I , i!y prepared for reduction, was tested by the anal; 

 Qtaining varying amounts of arsenic, which, with the ex 



, . and 9, were unknown to the analyst (see Table 1 >. 

 No. 9 the arsenic was present as arsenic acid. In Nos. 5, 

 ad 9, the comparison was made with standards which had been kept 

 ■ months, and the reading of the bands was confirmed by the 

 idards obtained by development of the initial land- with ammonia. 

 We do not claim for the method, under ordinary circumstance 

 accuracy than from five to ten per cent. 



Analytical Notes. 



itizt I Paper. We have found that the prepared paper, if kept 



dry and away from the light, does not lose its sensitiveness to a great 



after several months. On long keeping there is apparently a 



: reduction to mercurous chloride, since an old paper after 



lent with hydrochloric acid and washing gives a Blight darkening 



with ammonia or auric chloride (for this test, see below). Although 



this change does not greatly influence the result, it is better not to use 



r which has been kept too long. 



trary to Goode and Perkin, 19 we have found no advantage in 



using men-uric bromide instead of the chloride. Neither the aqueous 



ition of the former, which is, in addition, too dilute, nor the alco- 



>] ut ion, gives a paper of greater sensitiveness than that prepar id 



from the chloride. The alcoholic solution of the chloride, since it 



i more rapidly, leaves a less even surface of the salt npon 



the paper than is obtained by the slower evaporation of the aqueous 



in 



In case it is necessary to examine larger quantities of 

 'i for arsenic, a larger reduction bottle will naturally suggest 

 In this case, slight variation- from the procedure may be found 

 . and the absolute delicacy of the method may be some- 

 what 



ve found no sign of arsenical contamination from the rubber 



ed in the apparatus, and we have therefore not lessened the 



simp; iparatus by making it entirely of glass. The stop- 



! with dilute alkali and washed before D 

 19 Loc. cit. 



