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本刊1978年第1期刊载“几种标志溶液浓度的方法”(页13)一文后,曾收到读者来信多封,希望谈得更全面些,为此作如下之补充。ppm 或 p.p.m.(parts per million)系百万分之几的表示方式。从概念上说,它理应与%属同一范畴:所以实际上,并无 m/m、v/v 与 m/v 之分。它是专指 m/m 而言的。必须着重指出:它与容积 V 毫无关联。由于对这一点缺乏明确的认识,目前误认作 m/v的倾向相当普遍,因而造成 p.p.m.m/m 与 p.p.m.
We published a letter in 1978, No. 1, 1978, “Several Methods of Concentration of Marked Solutions” (p. 13). We have received many letters from readers and hope to talk more fully. This is supplemented as follows. ppm or p.p.m. (parts per million) is expressed in parts per million. Conceptually, it should be in the same category as%, so in fact, there is no m / m, v / v, and m / v. It refers specifically to m / m terms. It must be emphasized that it has nothing to do with the volume V. Due to the lack of a clear understanding of this point, the current tendency to misinterpret m / v is quite general, resulting in p.p.m.m / m and p.p.m.