Fatigue is one of the most common complaints brought to doctors, friends, and relatives. You’d think in this era of labor-saving and convenient transportation that few people would have reason to be so tired. The causes of modern-day fatigue are diverse and only rarely related to excessive physical exertion. Today, physicians report, tiredness is more likely a consequence of underexercise than of wearing yourself down with overactivity.
Physical fatigue is the well-known result of overworking your muscles. (46) Physical fatigue is usually a pleasant tiredness, such as that which you might experience after playing a hard set of tennis, chopping wood, or climbing a mountain. The cure is simple and fast: You rest, giving your body a chance to get rid of accumulated waste and restore muscle fuel.
(47) Illness induced fatigue is a warning sign or consequence of some underlying physical disorder, perhaps the common cold or flu or something more serious like cancer, while other symptoms are present that often suggest the true cause. Even after an illness passed, you’re likely to feel dragged out for a week or more. (48) Take your fatigue as a signal to go slow while your body has a chance to recover fully even if all you had was a cold. Pushing yourself to resume full activity too soon will certainly prolong your period of fatigue.
Emotional problems and conflicts, especially depression and anxiety, are by far the most common causes of prolonged fatigue. When such feelings are not expressed openly, they often come out as physical symptoms, with fatigue as one of the most common manifestations. (49) Understanding the underlying emotional problem is the crucial first step toward curing psychological fatigue and by itself often results in considerable lessening of the tiredness. Professional psychological help or career or marriage counseling may be needed.
There is a great deal you can do on your own to deal with both severe prolonged fatigue and those periodic washed-out feelings. You might try to do moderate exercise. (50) Contrary to what you may think, exercise enhances, rather than drains, engery and helps you to resist fatigue by increasing your body’s ability to handle more of a workload. At the end of a day exercise can relieve accumulated tensions, give you more energy in the evening, and help you sleep more restfully.
(48) Take your fatigue as a signal to go slow while your body has a chance to recover fully even if all you had was a cold.
（催化剂是氯化铝，氯化铝和加入的盐酸都有较强的腐蚀性，生产过程中产生大量废液、废气） 
2CuO CuO+2HNO3（稀）=Cu(NO3)2+H2O 
2Ni(OH)2+Cd(OH)2 已知Ni(OH)2和Cd(OH)2均难溶于水但能溶于酸。在酸性土壤中这种污染尤为严重。这是因为_______________________。 
