精美短文 第39篇:Oil and Water油和水
WordPress数据库错误： [Got error 28 from storage engine]
SELECT SQL_CALC_FOUND_ROWS wp_posts.*, yarpp.score
FROM wp_posts join wp_yarpp_related_cache as yarpp on wp_posts.ID = yarpp.ID
WHERE 1=1 AND yarpp.score >= 1 and yarpp.reference_ID = 100733 AND wp_posts.post_type = 'post'
ORDER BY score DESC, wp_posts.ID ASC
limit 10
Oil and Water
To understand the emulsifying process, we must first accept the scientific principle that oil and water do not naturally mix. Quite literally, they find each other’s presence repulsive. A good illustration of this aversion is homemade oil and vinegar salad dressing.When you shake or beat your salad dressing, you do more than disperse the oil throughout the vinegar: you also break down the oil into droplets minute enough to remain temporarily suspended in the vinegar (which from now on we will call water, because that tart condiment is in effect mainly water). The second you stop agitating the dressing, the oil droplets start to combine into units too large to be suspended in the water, and thus slither their way upward, separating from the water in the process.
The oil rises to the top and the water sinks because oil has a lower specific density than water. If you want a stable emulsion, you need an emulsifying agent which prevents the oil droplets from combining into larger units. Emulsifying agents occur naturally in many animal substances including egg yolks and milk. An emulsifying agent helps to keep the oil particles from combining in three basic ways. First, the agent coats the oil, serving as a physical barrier between the droplets.
Second, it reduces the water’s surface tension, which, in turn, reduces the water’s ability to repulse oil. Third, the agent gives the surfaces of the oil droplets identical electrical charges; since like charges repel each other the droplets repel each other.
油和水
为理解乳化过程的发生，我们必须首先认识到这样一条科学原理：水和油不能自然混合，它们实实在在互相排斥。 家制的油醋沙拉调料就是一个好例子。 当你搅拌沙拉调料时，你不仅使油扩散到醋里，而且使油滴被搅得很小可以悬浮在醋中( 自此我们改称它为水，因为事实上这种酸性调味品的主要成份就是水)。 一旦你停止了搅动，油滴就会凝聚，大到再也不能悬浮在水中时，它们就向上滑动出来而与水分离了。 因为油的密度小，所以油会浮在水上。如果想得到稳定的乳化，就需要一种乳化剂。它可以不让油形成大的油滴。
自然界中，很多动物体中含有乳化剂，如蛋黄和牛奶。 乳化剂可以从以下三方面阻止油滴凝聚。 一、 乳化剂包裹住油滴，在油滴间形成一道物质屏障。 二、 乳化剂降低水的表面张力，从而降低了水排斥油的能力。 三、 乳化剂使油滴表面带上了同种电荷，因为同种电荷互相排斥，油滴之间也相互排斥。
NSDA“SDcamps”全国英语演讲与辩论大赛（大学组）/SDcamps全国中小学生英语演讲与辩论大会（中小学及幼儿组）/美式辩论赛（以下简称大赛/大会）现诚招全国省市合作伙伴或城市合伙人，共同进行推广NSDA赛事品牌、举办赛事及培训活动、开展素质教育、美式营地项目等多方面合作。
我们希望认同NSDA理念，有赛事组织经验，或有教育资源，特别是有理想有热情的机构或个人一起携手，共同推广NSDA品牌、赛事及素质教育。以机构的形式，或以城市合伙人的方式均可。具体的赛事组织、盈利模式，欢迎电话或微信咨询。
微信：0012133598196
