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1048 CHAPTER 42 1957 Guide Phyla Algae Fungi Table 3. Principal Slime Formers Rough Division op Phyla Single celled, sometimes forming slimy sheets. Many celled in either sheets or fronds. Bacteria (Schizomycetes) frequently forming slimy surface coatings. Slime Molds (Myxomycetes) forming slimy sheets as one stage of their life history. Sac fungi (Ascomycetes) of which one division, the yeasts, occasion ally form slimy aggregates. The alga-like fungi (Phycornyceles) and the stalked fungi (Basidomycetes) rarely form slimes but their filaments may hold together the slimes of other organisms. All thallophyta are of universal distribution and many of them are slime-forming. Of the five divisions of algae, only three (the green, the blue-green, and the diatoms) are found in fresh water. Of the five di visions of fungi, all may occur in fresh water, the principal slime formers being indicated in Table 3. The methods of analysis commonly used in the sanitary examination of a water have, as their principal object, to identify and count pathogens. Most slime-forming organisms are not pathogens. When a water is subjected to a biochemical analysis for the purpose of evaluating its slime producing characteristics, tests, widely different from sanitary bacterio logical tests, must be made. Tests upon the water itself are seldom satis factory, and true indications of the sliming characteristics of a water can only be determined by the analysis of deposits on surfaces having a tem perature that approximates the operating temperature range of the final design equipment. The results of such tests are commonly used for select ing proper preventive measures. Slime and algae micro-organisms are capable of rapid multiplication and. if not controlled, can cause shut-down or permanent damage to equipmentThey can be controlled by chemical treatment of the water or in certain cases by mechanical cleaning of the surfaces affected. The chemicals used are usually toxic, and should therefore be handled only by trained personnel having a full understanding of the quantity required and their effect on operators as well as surfaces. Chemical treatment is usually preferred to mechanical cleaning par Table 4. Data Typifying the Deleterious Gas Content op Different Atmospheres Aib Floe Gases Name of. Gas Chemical Rcbal Metro politan Bitum. Coal Fuel Oils Formula Partial Partial Partial Partial % by Vol ume Pres %by sure Voir ume Pres sure % by Vol ume Pres sure % by Vol ume Pres sure paift psia psia psia Natural Gas % by Vol ume Partial Pres sure psia Oxygen................ Carbon Dioxide... Sulphur Dioxide.. o*: CO* so* 21 3.143 21 3.143 0.03 0.004 0.06 0.009 None None 0.003 0.004 2 15 0.07 0.299 2.245 0.010 7 13 0.03 1.048 1.946 0.004 10 10 0.0001 1.497 1.497 0.0015 | Corrosion and Water Formed Deposits, Causes and Prevention 1049 ticularly where surfaces are inaccessible for cleaning or where a shut-down of the operation is necessary for mechanical cleaning. Condensates .- All condensates are caused by the cooling of vapor. Condensates result ing from the cooling of water vapor in air are dews, sweats, rain, and snow, while those formed in steam-condensing apparatus are termed^ condensates or return water. In the heating and ventilating field, the biological characteristics of condensates are likely to be of concern only where the condensate is used Fig. 1. Solubility op Gases at Partial Pressure op 1 Psi as cooling water in recirculating systems. The deleterious gas contents of condensates, however, very often create serious corrosion troubles. The data in Table 4 typify the chemical composition of the atmosphere in rural and metropolitan areas, and of stack gases when various types- of common fuels are used. The curves in Fig. 1 disclose the solubility of the major deleterious gases'present in such atmospheres, in otherwise pure water, when the partial pressure of the gas is one psia. The most common deleterious gases entrained by steam are oxygen and carbon dioxide. In rare instances, hydrogen sulphide, sulphur dioxide, or ammonia are present. In most steam condensing equipment,7-8 the non-condensable gases entrained with steam accumulate so that the amount present in the vapor space is several hundred times higher than in the incoming steam and