The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

ly as iron sulphate, resulting from oxidation of iron pyrites, and having the same action as sulphuric. acid. Iron bicarbonate is a very unstable compound quickly giving off its ex- cess carbonic acid and, upon absorb- ing oxygen, is converted into iron rust. This is the reason for the pronounced red color in certain waters when exposed to air. 13. Suspended Matter—May be or- ganic or inorganic. Its presence de- pends upon the source of the water supply. Surface supplies frequently have large proportions of suspended matter, particularly after heavy rain- fall. All dirt and sediment carried as suspended matter in the water will have a tendency to cause foaming and priming. It forms scale only by being cemented to the boiler by other mate- rials. Scale Formation and Prevention There have been a great many authoritative statements as to the cost, in losses, of scale on the heating surfaces of boilers. It is not the in- tention to quote any of them. It is assumed that the reader will already have recognized the very severe effects of boiler scale formation as_ repre- sented in costs of flue and staybolt renewals, fire box sheet repairs, coal consumption, boiler failures, ete. It may be noted, however, that’ an error commonly made by those who attempt to calculate, mathematically, losses in boiler efficiency due to scale, is failure to make allowance for the location of the scale in the boiler. Since, in a boiler of the locomotive type, the fire-box area is responsible for most of the heat transmission, seale of given thickness in the heating surfaces of the fire-box will have a far greater effect on actual fuel con- sumption than will that on the flues and tubes. On the other hand, the actual rate of transfer of heat from gases to water through the heating surfaces represented in the tube area farthest from the fire-box, is so low that its complete insulation would have little effect on the amount of fuel actually consumed. In general the same differentiation must be made in estimating effect on maintenance costs due to overheating on account of insulating scale forma- tions. Some kind of treatment to combat scale formation is warranted when the water contains more -than eight grains of hardness per gallon. The kind of treatment best adapted depends upon the conditions. The in- telligent man of technical knowledge combined with practical experience in the chemistry of waters, and in boiler operation, weighs very carefully all of the conditions and all of the argu- ments for and against any single method of water treatment, before making a decision. Treating plants located at water supply stations are quite extensively used. Their installation involves rather heavy capital expenditures. Their operation involves the use of chemicals the nature of which is limited principally to soda ash and lime. In some circles there is a fixed and erroneous impression that the water from these treating plants is purified. The contrary is the case. The water treatment engineer has by the operation of the treating plants, substituted solids, remaining in solution, for the scale forming solids, which are settled out. MMMM Good Boiler Feed Water ORMATION of scale and corro- sion are constant enemies of ef- ficient operation and long life of marine boilers. Impurities in boiler feed water are the cause for both of these difficulties and ways and means of overcoming the injurious effect of such impurities have been proposed frequently. The present article care- fully analyzes the whole problem and the recommendations for treat- ment depends on the conditions of service. Treatment of boiler water should not be done by guess. The water should be properly analyzed for harmful mineral compounds and the proper kind of corrective should be introduced under competent techni- cal supervision to determine the kind and amount. Every marine engineer will find a great deal of valuable information upon this per- plexing problem in this article by Commander Wilson. UETUTNTTTUTVTRTTTTTTTVEEETUTUERTEETUUTEAUTUOUTTA CLUE CUGHEELUOGGHLLGGUOeEULUUGEEOPLOLCGOUOLULUGCOOEELULCCGLTLULCOOCoD EL The solids which remain in the water after wayside treatment, are those which cause foaming and pit- ting, when concentrated by boiler evaporation. It will be observed, therefore, that capital expenditure for treating plants, and the decision to operate them should be based upon the assurance gained by careful in- vestigation, that the advantage gained by the elimination of the scale form- ing solids alone, is sufficiently great to warrant; (a) cost of the treating plants; (b) cost of the required chem- icals; (c) cost of methods required to reduce the foaming tendency of the treated water. When the above conditions are met it is believed that treating plants are a desirable item in the equipment of modern hard-water district, power plants and vessel supply stations. Un- der all other conditions, it is be- lieved that the direct use of proper- ly worked out water’ treatment MARINE REVIEW—July, 1929 chemical compounds, in the boilers or supply tanks, is the most economical, efficient and best adapted method of boiler water treatment. It is for this reason that applica- tion of boiler water treatment com- pounds at the supply tanks, as the water is pumped, is sometimes ad- vocated. By this method no reaction takes place, or is expected, until the water has been passed to the boilers. The resulting reaction in the boilers is exactly the same, by this method, as would be obtained by applying the compound to the boilers them- selves. Sometimes when a_ very large amount of water is required from one source of supply and where that water is used only and entirely in boilers for steam making purposes, it is desirable to have the compound put into the water by the pumpers in- stead of by those operating the boilers. Wide Range of Boiler Compounds In the development of water treat- ment compounds for application di- rectly to the boilers or tanks, there is no such limitation in available chemicals as is the case with the out- side treating plant. On the contrary, these compound formulae run through a wide range of raw chemicals of known merit for certain desired effects. They also range through many forms allowing of selection for units of weight and measure such as sticks, briquettes, slabs powders and liquids. In designing these compounds, not only laboratory analyses should.be the guides, but consideration for ease of application, avoidance of waste, and greatest accuracy under adverse con- ditions must also be given. For various and obvious reasons when water treatment chemical com- pounds must be purchased and stocked in large quantities and issued for use under widely varying conditions, some- thing in the nature of an “all-purpose” material must be adopted. Such is the problem of the United States navy which operates steam boilers in all parts of the world. A compound formula was adopted some time ago, to meet as nearly as pos- sible these conditions. The theory was to have in the same compound each of the better known reagents in a fixed proportion and then meet the varied water conditions by using what would be, under other methods, an excess quantity of the compound in order to gain the desired reaction from the particular reagent in the compounds, upon the predominant im- purity in any particular water. Econ- omy by standardization in purchase, 27