这里翻译为40.0g,可以理解为称量的精密度。

非常感谢各位同仁,里面有一句”每次都要抽干”没有翻译出来,我不知道怎么翻译或者是否需要翻译出来.我总结了一下,修改成了如下的内容:
Dissolve 40 g of sample in boiled and cooled water. Allow to cool. Transfer this solution to a 1000ml volumetric flask and dilute to mark with the same water. Label as solution A. Pipet 20ml of solution A to a 500ml volumetric flask and dilute to the mark with the same water. Further pipet 20ml to a 100ml beaker, add 1 drop of methyl red indicator, then add acetic acid until the solution becomes light-red. Heat to 40ºC, then dropwise add 8-9ml of 0.1mol/L sodium tetraphenylborate -ethanol solution with agitating in 5 minutes. Allow to stand for 10 minutes. Filter the mixture with a G4 glass crucible pre-dried to a constant weight. Wash the sediment 8-10 times with each 5-ml of potassium tetraphenylboron saturated solution. Then wash the sediment o ne times with 2ml of anhydrous ethanol. Dry to constant weight at 120±5ºC.

The 精密度 of 40.0g is 10 times higher than that of 40g mentioned in the original!

This is the restriction to the translator. Even the origin is inappropriate or even incorrect, we have to translate exactly based on the original; what we can do is to add a remark “原文有误, 应是……”, or “原文可商榷, 建议……”

As far as I can recall from the demonstration by my chemistry teacher, she took Na from a bottle (it was immersed in some kind of oil) as quickly as possible; otherwise, it would be burnt in the air. I am not sure whether 迅速 is a critical operation in 用称量瓶称取样品40g, if positive, the word 迅速 should be translated.

Furthermore, from the original, 迅速 is not used to describe dissolve, therefore "Dissolve rapidly" is inappropriate).

实际上，我通常认为，这个dissolbe 已经包含了称取的过程。
这个迅速，英文里面也不是很多见的（我见到的）

汗颜。有时候我会按经验把原文里面没有体现出来的东西在译文里面体现出来，而有些原文里面有的东西，在译文里面因显得累赘而去掉。比如本篇里面的“抽干”。

Agree. We should be as close as possible to the original idea. Each word contains some meaning in the operation. Some chemicals may absorb moisture during weighing and need be weighed promptly as metal Na.