SOME NOTES ON ANCIENT MORTAES. 41 



mortar was carefully examined by Mr. John Spiller, F.C.S., 

 and he stated in his paper which appeared in the " Chemical 

 News " ^ that the probable arrangement of the constituents 

 might be considered : — 



Per cent. 



Sand 45-95 



Brick particles . 0-53 



Alumina . 3-00 



Peroxide of iron ....... 0*48 



Carbonate of lime 27 '73 



Silicate of lime lo'19 



Sulphate of lime 0*63 



Carbonate of magnesia ...... 1'59 



Water and loss 4*90 



This mortar was originally made up of about three parts 

 by weight of sand to one part of dry lime. In modern 

 practice it is usual to employ more sand and less lime. 



Mr. Spiller found that after extracting as much silica as 

 possible by means of dilute hydrochloric acid that the 

 residue yielded nearly 11 per cent, of silica to cold dilute 

 sodium hydroxide. Under similar treatment with cold soda, 

 builder's sand and pulverized flints yielded a mere trace of 

 silica in solution, whilst mortars 20, 100 and many hundreds 

 of years old yielded quantities of silica increasing with the 

 age of the mortar. It was suggested by Mr. Spiller that 

 perhaps the Romans used a pozzuolana in compounding their 

 mortar, or perhaps this soluble silica, or silicate, is the 

 direct result of long contact of plain sand and lime. 



It is interesting to note that a sample of mortar from the 

 square Roman bath at Bath contained fully as much soluble 

 silica as the mortar from the Roman wall found in London. 



The pozzuolana found in the neighbourhood of Puteoli, 



1 " Chemical News," 1888, p. 189. 



