224 
The Philippine Journal of Science 
1919 
The data given in the first two tables may be readily under- 
stood by reference to fig. 1. The setting time of each sample 
is plotted against the sulphuric anhydride content. The plant 
samples are designated by Q and the laboratory samples by +. 
The line representing sixty minutes, the minimum initial set 
allowable under Government specifications when Gillmore nee- 
dles are used, and the lines representing 1.80 per cent and 
2.10 per cent sulphuric anhydride, respectively, are made heavy 
for the sake of comparison. The last named is the upper limit 
of sulphuric anhydride content allowable under Government 
specifications. 
SPECIAL PLANT TEST 
By referring to fig. 1 it will be noted that only four plant 
samples below 1.50 per cent were included. Cement had not 
been regularly manufactured below this amount, and no such 
Per cent sulphuric anhydride. 
/ 2 3 
Fig. 1. Showing the relation of initial set to sulphuric anhydride content. 
plant samples were available. The first cement was made with 
1.50 per cent sulphuric anhydride but was found unsatisfac- 
tory, and since then the calculated amount had been gradually 
