chemicals

• This chemical change can be expressed by an equation .
  我们可用反应式表示这种化学变化。
• The chemicals used in the experiment must be very pure .
  用于这一实验中的药品必须很纯。
• These chemicals are difficult to remove from water .
  要从水中清除这些化学物质是困难的。
• They differ in solubility and chemical reactivity .
  它们在溶解度和化学反应活性上有差别。
• Chemical constantly circulate or recycle in the system .
  化学物质在系统中不断循环或回流。
• Growers must be prepared to use a range of chemicals .
  栽培者必须准备使用一系列的化学药剂。
• Water is the most abundant chemical compound in the biosphere .
  水是生物圈中最丰富的化合物。
• The state allotted them large quantities of chemical fertilizer .
  国家给他们调拨了大量化肥。
• Oxygen is often used as reactant in chemical processes .
  在化学过程中，氧气经常充当为反应物。
• Attention should be given to recovery and reuse of chemicals .
  应当注意化学品的回收和再利用。