June, ’24] 
ROBINSON: SKIM MILK EMULSIONS 
399 
pecially if hard water is used. It may be necessary to use more lime 
than advised above if the water is very hard. Whole milk or milk 
powders may be substituted for skim milk. The dried milk should be 
used at the rate of 2.5 ounces for each quart of milk necessary. 
Several grades of mineral or lubricating oil were used and no difficulty 
was experienced in obtaining good emulsions with any of them. The so- 
called red-engine oil is recommended mainly on account of its low cost. 
The light or medium grade will give best results. 
Burroughs and Grube 4 used commercial calcium caseinate, which is a 
mechanical mixture of about one part casein and two parts hydrated lime, 
as an emulsifier with excellent results, but were not so successful with 
milk. If, however, they had first added an excess of lime to the milk 
before using, they would not have experienced any difficulty. In fact, 
the milk emulsified easily a waste, crank-case oil but it was impossible to 
emulsify it with calcium caseinate. After the addition, however, of a 
small amount of commercial cresylic acid to the dissolved casein a good 
emulsion was obtained. 
It was observed that under certain conditions a water-in-oil emulsion 
was formed instead of the oil-in-water emulsion which may be diluted 
with water without destroying the emulsion. This often happens when 
the proportion of water to oil is reduced. In order to facilitate the 
preparation of emulsions various materials were added to the emulsifiers 
to augment, if possible, their emulsification powers. Among the ma¬ 
terials that apparently improved the emulsifying powers of milk and 
calcium caseinate were commercial cresylic acid, sheep dip, beechwood 
creosote, and creosote oil. It is recommended that about an ounce of 
commercial cresylic acid be added to the water in the formula given 
above. 
The Use of Skim Milk as a Spreader. The work by Lovett 5 
on casein as a spreader suggested the possibilities of using milk as a 
substitute. Since casein is prepared from milk it is natural to expect that 
the latter likewise would have good spreading properties. Observations, 
however, made by spraying lead arsenate in diluted milk suspension, on 
apples and various leaves showed that there was no appreciable spreading. 
Instead the spray assumed the droplet form on the surface similar to 
water. Later, in a study of the surface tension of various spreader 
materials, milk showed low values indicative of a good spreader. Fur¬ 
ther study showed that very fresh milk would spread well on all. sur¬ 
faces on which calcium caseinate would spread, but after a slight de- 
6 Ore. Experiment Station Bui. 169, 1920. 
