I 



W ASlUN'c; I'OW HDERS FOR DAIUV USE 185 



Olher hujredieiitu are i)ften added for specilic i)uri)()se.s. JIi/ptx-hlDriles arc 

 added in some instances because of their germicidal action. Sulfates are 

 occasionally added, l)iit have no desiral)le qualities. Siliciite.i of scjme 

 niet^^ls are added to render protection to the machinery parts in contact 

 with the solution. SodiuDi ziiirate and nlumiuate are sometimes added 

 for' protection of zinc and aluminum jiarts respectively. Rentiinles and 

 r/HHf.s- are also occasionally found in the powders and are usually added to 

 ]>rotcct cojtper fittings. Grit is added to some to clean metafs. liornx, 

 although not often found, has certain advantages of emulsification and 

 disinfecting powers. 

 Thus it may be seen that no one ingredient is a perfect wasliiiig <'om]»oiiiKl 



of itself, and for efficient washing- a mixture should be used. 



General Considerations 



Soap, owing to the difficulty of rinsing which is due in large measure to 

 suds formation, and owing to the dangers from odor, is not considered a wise, 

 nor is it an essential ingredient for washing powders for dairy use. Also it 

 is more expensive and will deteriorate upon long standing. Powders contain- 

 ing soap are light in weight and thus often deceive the purchaser as to the 

 quantity he is obtaining. 



For hand washing any free caustic should be avoided because such solu- 

 lions readily attack the skin of the operator. It also attacks metals and in 

 general its use is not justified, for other ingredients of less drastic action are 

 e\en more efficient in the actual cleaning operation. Caustic lacks many of 

 the essential qualities of a good cleaning agent. It is very difficult to rinse off 

 and thus will cause pitting and darkening of .the cans. 



For machine washing strong caustic may be used and is efficient in removing 

 grease. Although it acts upon metals and glass the action is not drastic and 

 is noticed only after continued use. The mechanical washer is perhaps the 

 most efficient because of the possibility of using stronger solutions and hotter 

 water. A 3 per cent caustic at 140° F. can be used with the mechanical 

 washer. 



Tri-sodium phosphate is a particularly valuable constituent because of its 

 remarkable emulsifying and softening power. In softening water containing 

 calcium sulfate, calcium, magnesium and iron silicates and calcium carbonate 

 the action is to throw all these metals out of solution as phosphates while the 

 acid radicals will become united with sodium and remain in solution where 

 they will cause no harm. The phosphate also has a strong buffer effect which 

 keeps the caustic strength of the cleaning solution uniform by supplying more 

 caustic as soon as some is neutralized. The caustic strength of the phosphate 

 is only about one-tenth that of an equal amount of hydroxide and therefore 

 no great caustic concentration is necessary at the start of operations in order 

 to have the solution strength maintained during the washing when the phos- 

 I^hate is used. In this respect, using phosphate, added in quantities at the 

 start, gives the same effect as adding a small amount of hydroxide every 

 little while. 



Casein is soluble in alkali in ])roportion to the caustic strength. However, 

 nmch of the precipitated or baked-on casein is in the form of calcium casein- 

 ate which is insoluble in alkali. Here tri-sodium phosphate acts to a much 

 greater advantage than the other components. Calcium in the water supply 

 is more efficiently removed by sodium phosphate. Casein is soluble in borax 

 although this substance is scarcely ever used in dairy w^ashing powders. It 

 would aid the disinfecting properties but it has only a mild cleansing action. 

 P>()rax is easily rinsed and fornss a good emulsion with milk fats. 



