铅笔是人们再熟悉不过的学习用品.我们常用的铅笔(见图1)笔杆上一般都标有不同的标志,如“HB”、“2B”等.那么,铅笔上的这些标志有什么含义呢?有关铅笔的由来还有一段传说.1564年,在英格兰一个叫巴罗代尔的地方,人们发现了一种黑色矿物——石墨.当地的一些牧羊人发现可以用石墨在羊身上画记号.受此启发,人们把石墨块切成小条拿来写字和绘画,但石墨条很容易弄脏手,而且容易折断.1761年,德国化学家法伯尔解决了这个问题:他先把石墨矿石研磨成粉末,用水洗去杂质获得纯净的石墨粉,接着又在石墨粉中掺人硫黄、锑、松香等物质,然后再将这种混合物加热凝固,并压 Pencils are familiar school supplies. Our commonly used pencils (see Figure 1) are marked with different signs on the pen, such as “HB”, “2B”, etc. Then, these flags on the pencil What does it mean? There is a legend about the origin of pencils. In 1564, in a place called Barrodale in England, people discovered a black mineral - graphite. Some local shepherds found that they could use graphite in sheep. Marked on the body, inspired by this, people cut the graphite blocks into small strips for writing and painting, but the graphite strips are very prone to soiling and easily broken. In 1761, the German chemist Faber resolved the problem: he The graphite ore is ground into a powder, washed with water to remove impurities to obtain pure graphite powder, and then the graphite powder is mixed with sulfur, hydrazine, rosin and other substances, and then the mixture is heated and solidified, and pressed