182 TECHNICAL BULLETIN 13 



and those containing soap. Ihe roles played by the various ingredients will 

 be discussed later after the practical tests have been described. 



The water content of the powders varied considerably. No determinations 

 of moisture content are given because this factor would tend to vary. 

 Pcvwders high in sodium hydroxide would tend to absorb water more rapidly 

 than others. All the powders when weighed were of a dry, somewhat dusty 

 nature, and not in the least gummy or sticky. 



The ease of solution of the powders followed a general trend depending 

 upon composition. Those containing tri-sodium phosphate were aH very slow 

 to dissolve. Also, the soapy powders were somewhat slower to enter solution 

 and often lumped. The carbonate and hydroxide powders dissolved quite 

 readily although there was a tendency for the hydroxide powders to lump. 

 Those high in sodium hydroxide tended to heat considerably upon dissolving 

 and those high in tri-sodium phosphate tended to cool. 



Practical Tests 



In this part of the investigation it was aimed to duplicate actual working 

 conditions in the laboratory and then to conduct practical tests in the plant. 

 The tests used and the method of procedure for each are given below. 



The strength of solutions employed in these tests was standard 0.6 per cent 

 based on the dry powder. Ihis was found to be the average concentration 

 recommended by the various manufacturers. A few reconuuend a weaker 

 or stronger solution, but in order to study the efficiency of the powders a 

 standard had to be adopted. Ihis concentration corresponds to five pounds 

 of powder to one hundred gallons of water. 



The water softening power of the powders was determined by treating 

 lOOcc portions of the samples with 50cc quantities of standard hard water 

 and then adding standard soap solution until permanent bubbles appeared. 



The washing power of the powders was deteniiined by tests on unifoniily 

 dirty bottles. Five cubic centimeter c]uantities of milk were run into bottles 

 and allowed to dry. While drying, the bottles were occasionally tilted and 

 rotated so as to wet the sides. The action of lOOcc amounts of the cleaning 

 solutions upon these dirty bottles was then observed. 



The emulsifying power was tested by shaking a lOOcc portion of the powder 

 solution with l.Occ of butterfat, the whole contained in a tall cylinder. The 

 degree of emulsification was determined bj' the whiteness of the emulsion and 

 by the length of time the enmlsion persisted. 



The ease of rinsing of each solution was tested by moistening the fingers 

 with the solution and then counting the numiber of half seconds the slippery 

 feel lasted while the fingers were held under a flow of water and gently 

 rubbed twice per second. The flow was from a faucet and was regulated to 

 give a stream one-fourth inch in diameter. This test was found to be satis- 

 factory and gave consistent and reproduceahle results. The average time of 

 three experiments was taken in each case. 



The action of each washing powder solution upon the metals aluminum, 

 copper, nickel, tin and zinc was also studied. Strips of these metals were 

 cleaned and allowed to stand in solutions of the various powders. These 

 tests were run for a considerable length of time in order to determine the 

 effect of continued use of the powders. 



All results are tabulated below. In case tlie figures given seem to show 

 some discrepancy the reader is reminded that the tests are not absolute, and 

 the previous workers on similar tests for washing efficiency obtained values 

 varying as much as 10 per cent. 



