ASSAY OF ARSENICAL DIPPING FLUIDS. 17 
The directions for executing the test read as follows : 
1. Use regular outfit. Measure25c. c. of bath into wide-mouth bottle and add 1 blue 
tablet. When entirely dissolved, add 1 red tablet, and after this has entirely fallen to 
powder gently but continuously swirl the bottle for 3 minutes, then let it stand for 7 
minutes more with an occasional mixing. 
2. Next add test fluid from the graduate until the blue color just remains perma- 
nent for at least 10 seconds throughout the whole of the well-mixed liquid. Add but 
a few drops at a time toward the end and avoid excess, but pay no attention to the 
actual volume of test fluid added at this stage. 
3. Now add two white indicator tablets and agitate till mostly dissolved. Fill the 
graduate to upper mark (zero) with test fluid, adding it just as in the estimation of 
"actual arsenious oxid" until the blue color just reappears permanently, avoiding 
excess. 
The number of cubic centimeters of test fluid thus added to bring back the blue 
color represents hundredths of 1 per cent of "total arsenic" in the bath. 
If "oxidized arsenic" is present in only very small amount the 
results are likely to be somewhat low, owing to some formation of 
arsenious sulphid, but in any event such small amounts of "oxidized 
arsenic' ' are without significance. Again it is obvious that the 
quantity of thiosulphate used will not show the presence of "oxidized 
arsenic" in amount much over 0.2 per cent of the bath, but this 
appears amply sufficient, for if so much is present, in addition to the 
actual arsenious oxid, which of course is determinable in practically 
any amount, the bath certainly should not be used for dipping. 
THE INTERPRETATION OF RESULTS. 
The " standard arsenical solution" is recommended by the bureau 
for use in two strengths — first, 10 pounds of white arsenic and 25 
pounds of sal soda to each 500 gallons, and, second, 8 pounds of white 
arsenic and 24 pounds of sal soda to each 500 gallons of bath. The 
theoretical percentages of arsenious oxid will therefore be prac- 
tically 24 hundredths of 1 per cent for the 10-25 formula, and 19 
hundredths of 1 per cent for the 8-24 formula. Practical experience, 
however, has shown that the baths work with perfect satisfaction 
so long as the percentages of "actual arsenious oxid" do not drop 
below the following limits: For the 10-25 formula, 22 hundredths 
of 1 per cent; for the 8-24 formula, 175 thousandths of 1 per cent. 
These figures therefore represent minimum percentages below which 
the contents of the respective baths in " actual arsenious oxid" 
should not be allowed to fall. The maximum allowed percentages 
of " actual arsenious oxid" should be but little above the theoretical 
figures; say, 25 hundredths of 1 per cent for the 10-25 formula and 
20 hundredths of 1 per cent for the 8-24 formula. 
Respecting the maximum allowable percentages of "total arsenic," 
it is not yet possible to make any statements based upon positive 
experimental evidence. One might tentatively set the following 
limits which experience has indicated to be within the margin of 
safety: 30 hundredths of 1 per cent for the 10-25 formula; 25 hun- 
dredths of 1 per cent for the 8-24 formula. 
O 
