. Transactions - American Society of Heating, Refrigerating and Air-Conditioning Engineers. FIG. 3. CUT-AWAY VIEW OF DE-AERATING DEACTIVATOR,SHOWING CONSTRUCTION sarily indicate that such a water will precipitate any scale forming pro-tective coating in the pipes and boilers unless the carbonates be presentalso. It will be seen that soft waters and such hard waters as contain smallquantities of bicarbonates are not scale forming in ordinary hot watersystems and do not therefore tend to protect against corrosion in this way. The foregoing gives a fair idea of the relationship between the chemi-
. Transactions - American Society of Heating, Refrigerating and Air-Conditioning Engineers. FIG. 3. CUT-AWAY VIEW OF DE-AERATING DEACTIVATOR,SHOWING CONSTRUCTION sarily indicate that such a water will precipitate any scale forming pro-tective coating in the pipes and boilers unless the carbonates be presentalso. It will be seen that soft waters and such hard waters as contain smallquantities of bicarbonates are not scale forming in ordinary hot watersystems and do not therefore tend to protect against corrosion in this way. The foregoing gives a fair idea of the relationship between the chemi-cal properties of the water and the subjects of incrustation and corrosion,. Discussion of Hot Water Heating Devices for Domestic Service 185 from which it may be seen that a good chemical analysis of the water isa very helpful factor in designing a hot water system. As the author has stated and as has previously been demonstrated onnumerous occasions by the leading authorities, who are making a studyof this subject, practically all of the corrosive activity between the waterand the metals of a hot-water service system is due to the presence offree dissolved oxygen in the water. This action is sometimes intensifiedby the presence of chlorides as referred to above in the case of magnesiumchloride, or by the presence of appreciable quantities of free, dissolved,carbonic acid gas in the water. The action of this free carbonic acid gasis mainly along the lines of giving the water an acid tendency which pro-motes the electro-chemical corrosive activity much in the same way ashydrochloric acid, except in a much milder degree. In other words it is a well-established
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