tailieunhanh - IELTS reading and writing part 6

Tham khảo tài liệu 'ielts reading and writing part 6', ngoại ngữ, toefl - ielts - toeic phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Reading Passage 2 You are advised to spend about 20 minutes on Questions 16 - 29 which are based on reading passage 2. The History Of Aspirin ced Byer In the late 1890s Felix Hoffman a chemist with Germany s Company started looking for a new treatment to help relieve his fa s painful rheumatism. Drugs to treat the pain and inflammation of rheumatism had been around for 2000 years. In 200 . Hippocrates the father of medicine observed that chewing on the bark of the white willow tree soothed aches and pains. In 1823 chemists finally succeeded in isolating the bark s active ingredient. It was salicylic acid. The problem was salicylic acid wasn t safe. In its pure form it was so powerful that it did damage at the same time it was doing good. Unless you mixed it with water it would bum your mouth and throat. And even with water it was so hard on the stomach lining that people who took it became violently ill complaining that their stomachs felt like they were crawling with ants. Salicylic acid had given Hoffman s father multiple ulcers. He had literally burned holes in his stomach trying to relieve his rheumatic pain and was desperate for something milder. So Hoffman read through all the scientific literature he could find. He discovered that every scientist who had tried to neutralize the acidic properties of salicylic acid had failed except one. In 1853 a French chemist named Charles Frederic Gerhart had improved the acid by adding sodium and acetyl chloride - creating a new compound called acetylsalicylic acid. However the substance was so unstable and difficult to make that Gerhart had abandoned it. Hoffman decided to make his own batch of Gerhart s acetylsalicylic acid. Working on it in his spare time he managed to produce a purer more stable form than anyone had been able to make. He tested the powder on himself successfully. Then he gave some to his father. It eased the elder Hoffman s pain with virtually no side - effects. Hoffman reported hie findings to his