. The Architect & engineer of California and the Pacific Coast . e the engineering profession is be-coming convinced that acids in weak solutions are evolved from the de-composition of domestic sewage. From the kitchen there are a largeamount of fats, both from the dish water and from the hot water turnedoff from cooked meats. These Eats develop stearic acid which is very mildin itself but nevertheless has a disintegrating effect when imprisoned formany years in the pores of concrete. The usual domestic sewage containing considerable sulphur first formsa sulphuretted hydrogen compound 1LS. Thi
. The Architect & engineer of California and the Pacific Coast . e the engineering profession is be-coming convinced that acids in weak solutions are evolved from the de-composition of domestic sewage. From the kitchen there are a largeamount of fats, both from the dish water and from the hot water turnedoff from cooked meats. These Eats develop stearic acid which is very mildin itself but nevertheless has a disintegrating effect when imprisoned formany years in the pores of concrete. The usual domestic sewage containing considerable sulphur first formsa sulphuretted hydrogen compound 1LS. This H2S later becomes a sul-phurous acid 11 JS< )... which in itself is harmless to concrete and very mildin its action and is largely employed by paper manufacturers in their pulpdigestors which are usually lined with a very rich mixed concrete. Thesepulp digestors are not disintegrated by the three per cent solution of sul-phurous acid, as the paper manufacturers are very careful to see that ii l the faUunof concrete fir*- sanitarysewers of Alameda, Califor. 70 The Architect and Engineer remains in the sulphurous condition so as to properly cook the woodpulp. In the sewers this sulphurous acid H2S03, a little later developsinto a sulphuric acid, H=S04, and this is the acid that eventually causesthe disintegration of the concrete. This weak solution of sulphuric acidbeing imprisoned in the pores of the concrete attacks the calcium of thePortland cement, which upon being eaten away leaves the balance of theconcrete a mere core of sand, gravel, and rock. On the subject of the materials for pipe sewers the eminent sanitaryauthority, Rudolph Hering of New York, may be quoted. He writes: Due to the glazing of vitrified pipe, we get an advantage for them over cementpipes, which usually are not manufactured with an equal smooth surface. The structure of the material of vitrified pipe sewers does not change. What-ever it is when the pipe is examined at the point of delivery, it usual
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