26 ARSENIC IN PAPERS AND FABRICS. 



METHOD. 



In the case of wall papers, cut out a pattern measuring 4 inches by 

 3.25 inches (0.01 square yard) and in the case of dress goods a piece 

 measuring 12 by 10.8 inches (0.1 square yard). Cut up the piece so 

 obtained into smaller pieces and treat in a porcelain dish with 1 to 5 

 ec of a mixture of concentrated sulphuric acid and nitric acid (30 to 

 1). Allow the action to take place for a few minutes and add a few 

 drops of water, which from the heat generated will cause the paper to 

 be quickly attacked. Heat with a low flame until all of the sulphuric 

 and nitric acids are driven off, or at least until the residue has granu- 

 lated and the fumes of sulphuric acid become slight. Break up the 

 charred mass thoroughly, add a little water, and boil to get rid of 

 sulphurous acid. Filter through a small filter and wash to about 40 

 cc. Transfer this filtrate to the apparatus, which has previously been 

 prepared in the following manner. 



APPARATUS. 



This consists of a small flask witli a wide mouth, holding about 100 

 cc. Through one hole of a rubber stopper a separatory funnel passes 

 to the bottom of the flask. Through another hole in the rubber 

 stopper passes the exit tube, which is in turn joined to a Liebig bulb 

 containing a small amount of a solution of lead acetate to absorb any 

 selenium, tellurium, or sulphur. This in turn is joined to a calcium 

 chlorid tube, which is then attached to a long tube of very resistant 

 glass. This glass tube is drawn out at one point rather small, nearly 

 capillary, and the heat is applied about 0.5 inch before the drawn- 

 out portion. Heat with two Bunsen burners, neither of which plays 

 upon the glass directly but upon a piece of fine wire gauze wrapped 

 around the glass. When preparing this apparatus for use, add about 

 3 grams of arsenic-free granulated zinc to the wide-mouthed bottle 

 and then about 30 cc of arsenic-free sulphuric acid (I to 8). Let 

 the apparatus run for fifteen minutes, after which apply heat for 

 approximately twenty minutes to be sure that no arsenic is present.* 



The apparatus is now ready for the addition of the extract from the 

 wall paper or fabric previously mentioned. This is run in, and the 

 action is allowed to continue for one hour. The mirror thus formed 

 is compared with mirrors containing known amounts of arsenic, which 

 have been previously prepared with the same apparatus. The stand- 

 ard mirrors usually contain the following amounts of arsenic: 0.005, 

 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.065 (or 0.001 grain), and 0.07 mg of 

 arsenic. These mirrors should be in sealed tubes and be remade 

 about every three weeks, as they tend to fade a little upon standing. 

 When not in use they should be kept in a dark place. 



In case a larger amount than 0.07 mg of arsenic is obtained, that 



