May 12, 1923 
Effect of Decomposition on Concrete Tile 
479 
The results given in the preceding table are very remarkable. Not only 
did the new tile after a presumably thorough curing still contain 4 per 
cent of free alkali, but the old tile after 5 years in the ground, during 
which time it was partially destroyed, still contained nearly half as 
much. The importance of the fact indicated can hardly be overesti¬ 
mated. It will be discussed later. 
SOLUTION IN HCl 
New tile in concentrated HCl was then tested. Strong evolution of 
bubbles showed the presence of a considerable percentage of carbonate. 
The dried filtrate was ignited and treated again with acid. The exact 
percentage of solubility is shown by Table V. 
TablK V.— Percentage of new tile soluble in concentrated HCl 
Constituent. 
Percentages. 
Insoluble silica. 
47. 42 
52- 58 
3- 40 
49. 18 
Total soluble. 
Soluble silica.. 
Total solubles other than silica. 
ultimate solubility in organic acids 
In order to ascertain the percentage of the tile which might be ulti¬ 
mately soluble in organic acids and to establish a relation between it and 
the aggregate used, an acid of low hydrogen-ion concentration was 
chosen, namely, quarter strength acetic, and samples of the old and the 
new tile and the aggregate from which the tile were made were treated 
with it. The acid used was supposed at the time to be full strength, but 
was later found to be about 85 per cent. From each sample previously 
dried in the electric oven, 5 gm. was taken and boiled for 10 minutes 
in the dilute acid and the residue weighed after drying in the electric oven 
at 110° C. The results are given in Table VI. 
Table VI.— Percentages of old tile, new tile, and aggregate soluble in 21 per cent strength 
acetic acid 
Item. 
Old tile. 
New tile. 
Aggregate. 
Grams taken. 
5. 00 
•2. 2000 
5. 00 
3. 2777 
I. 7223 
34-45 
5. 00 
3-5152 
I. 4848 
29. 69 
Residue. 
Loss. 
0* 0'^'^ 
I. 6910 
33-82 
Per cent soluble. 
