362 The Philippine Journal of Science 1922 
aration of such impregnated fibers involved a study of the 
kind of fiber to be employed, the concentration of the solutions 
to be used, the length of time of dyeing, and the temperature of 
the bath. The fibers tested were wool, cotton, flax, silk, and 
viscose silk. The fibers were impregnated with a mixture of 
stannous chloride and pyrogallol. In a test solution of gold, 
the prepared fibers gave the following colors: Wool, blue to 
gray; cotton, pink; flax, silk, and viscose silk, dark red to violet. 
Irrespective of the color produced, viscose silk is the fiber best 
suited for use in microscopic qualitative analysis. The follow- 
ing tests were therefore made on viscose silk: Fibers were 
dyed for one, ten, and twenty minutes in cold and in boiling 
solutions of stannous chloride and pyrogallol. The concentra- 
tion of each of the two chemicals was varied from 1 per cent to. 
20 per cent. The best results were obtained in a solution of 
10 per cent stannous chloride and 10 per cent pyrogallol. The 
effect of the addition of hydrochloric acid to the bath was tested 
and is shown in Table 1. 
TABLE 1.—Color of impregnated viscose-silk fibers in gold solution prepared 
with varying concentrations of stannous chloride, pyrogallol, and 
hydrochloric acid. 
Concentration of chemical. a 
Time of 
Hydrochlo- prcigenorie OE SA root 
oesets. | Stpeaee terivanl|- hen, | ee 
ted. 
Per cent. | Per cent. | Per cent. | Minutes. 
0 5 10 10 | Pale red. 
1 10 0.1 10 | Very pale red. 
1 10 1 10 | Red. 
1 10 10 10 | Good red. 
5 10 10 10 | Very good red, 
Weakened fi- 
10 10 10 10 ber. 
0 10 10 10 | Color too light. 
5 10 20 10 | Good red. 
A bath containing over 5 per cent concentrated hydrochloric 
acid or 10 per cent stannous chloride tended to weaken the fiber. 
Immersion for more than ten minutes in 10 per cent stannous 
chloride solution seriously weakened the fiber. 
Stannous chloride made by dissolving 10 grams of tin in 100 
cubic centimeters concentrated hydrochloric acid and adding 10 
‘per cent pyrogallol gave a fairly good fiber when the silk was 
allowed to remain in the solution only one minute. Two minutes 
