184 TECHNICAL BULLETIN 13 



The Action of Washing Powders on Metals. 



Key 



E — Excellent condition 

 G — Good condition 

 F — Fair condition 

 P — Poor condition 

 B — Bad condition 



Tests of the germicidal action of solutions of the above samples showed 

 that in solutions of 0.6 per cent strength, dirty, milky water was sterilized 

 after standing for thirty minutes in all tests at room temperature. 



Plant tests were conducted upon representative powders by using them in 

 the daily bottle and can washing operations. The results in these cases sub- 

 stantiated those obtained from tlie laboratory tests. 



Summarizing, we may place the ingredients in the order of effectiveness as 

 follows: 



Water Softening Powers: Carbonate, phosphate, soap, hydroxide 



Washing Powers: Carbonate, hydroxide, soap, phosphate 



Emulsifying Powers: Soap, phosphate, carbonate, hydroxide 



Ease of Rinsing: Carbonate, phosphate, soap, hydroxide 



Action on Metals: Hydroxide attacks aluminum, copper and tin 



Carbonate attacks aluminum, copper and tin 

 Phosphate attacks aluminum 

 Disinfecting Values: All powders in strength ordinarily employed 



act as disinfectants to such a degree as to 

 make th,e washing solution sterile. 



The Role of Constituents Used in Cleaning 



Reviewing and correlating the data observed in the above experiments, it 

 is possible to draw somewhat trustworthy conclusions as to the roles played 

 by each jiarticular ingredient in the powder and tlieir action when combina- 

 tions are used. 



Sodmm Carbonate has very good softening power, greatly aids washing mech- 

 anism, is a poor enuilsifying agent, rinses very easily, has slow action on 

 tin and very mild action on hands, and neutralizes odors. 



Sodium Hydroxide is a very poor water softener, with good washing power 

 and poor emulsifying effect. It is very difficult to rinse, acts on metals, 

 has a severe action on hands, is a strong caustic, and will pit cans. 



Tri-Sodium Phosphate is an excellent water softener, with poor washing power 

 and excellent emulsifying properties. It is easy to rinse, has very mild 

 action on metals and hands, is a good solvent for casein, and gives buffer 

 effect which keeps caustic strength uniform. 



Soap has poor softening power, poor washing power and excellent emulsifying 

 properties. It is hard to rinse, has mild action on metals and hands, and 

 is apt to leave scum in bottles. 



