Downloaded from https://www.everyspec.com MIL-STD-81OC divided dense fog with the atomizer or atomizers used. TO insure against clogging ‘theatomizers by salt deposition, the air should have a relative humidity of at least 85 percent at the point of release from the nozzle. A satisfactory method is to pass the air in very fine bubbles through a tower containing heated water which should be automatically maintained at a constant level. The temperature of the water should be at least 35° C (95eF)A The permissible water temperature increases with increasing volume of air and with decreasing insulation of the chamber and the chamber’s surrOundfngs:
However, the temperature should not exceed a value above which an excess of moisture is introduced into the chamber (for example 43° C (109° F) at an air pressure of 12 psi) or a value which makes it impossible to meet the require- ments for operating temperature. 2.4 Preparation of-salt solution. The salt used shall be sodium chloride containing on the dry basis not more than O.1 percent sodium iodide and not more than O.5 percent of total impurities. Unless otherwise specified, a s *1 percent solution shall be prepared by dissolving five Parts by weight of salt in 95 parts by weight of distilled or demineralized water.
The solu- tion shall be adjusted to and maintained at a specific gravity between the ;, limits shown on figure 509.1-1 by utilizing the measured temperature and den- , sity of the salt solution. Sodium tetraborate (common borax) may be added tO the salt solution in a ratio not to exceed 0.7 gms (1/4 level teaspoon) sodium tetraborate to 20 gallons of salt solution as a pH stabilization agent. 2;4.1 Adjustment of pH of the salt solution shall be so maintained that the solution atomized at 35° C (95”F) and collected by the method specified in 3.1.3 will be in the PH range of 6.5 to 7.2. Only diluted C.P. hydrochloric acid or C. P. sodium hydroxide shall be used to adjust the PH.
The addition of sodium tetraborate as recommended in 2.4 will aid in maintaining a stable pH value. The pH measurement shal1 be made electrometrically,using # glass electrode with a saturated potassium chloride bridge, or by a calorimetric method, such as bromothymOl blue, provided the results are equivalent to those.obtained with the electrometric method. The pH shal1 be measured when preparing each new batch of solution and as specified in 3.1.4. 2.5 Filter.A filter fabricated of noncorrosive materials similar to that -in figure 509.1-2 shall be provided in the supply line and immersed in the salt solution reservoir in a manner such as that illustrated in figure 509.1-3.
509.1-3 B METHOO 509.1