一些称量问题的解决方法（摘自国外课题组）

不太专业，仅供参考



Troubleshooting: Weighing Reactants and Reagents



问题解答：称量反应物和试剂



Problem: I forget to tare my flask.

问题： 我忘记将烧杯归零了。

Solution: For all of your flasks, write the weight twice on the inside of the joint in pencil. The pencil will eventually rub off, but since the tare is written twice, having one blur is no problem. Then you can erase the other and re-tare, so the weight is always accurate.

解决办法：将你所有烧杯内外都用铅笔写上重量。铅笔最后会被抹掉，但是由于归零数据记录了两次，抹掉一个也没关系。之后你就可以擦掉另一个然后归零，所以称重总是准确的。



Problem: I need to weigh 0.5 mg of catalyst. The balance is not accurate for such small weights.

问题：我需要称量0.5mg晶体。天平没有这么小的精确度。

Solution: Make a solution of (say) 5 mg of the solid in (say) 1 mL of solvent, and then syringe out 100 microliters.

解决办法：将5mg所说的晶体溶于溶液中，比如说溶于1ml溶剂中，然后用注射器抽取

100μL。

Problem: I do not know the density of a liquid- how do I know how much to add via syringe?

问题：我不知道待称量液体的密度—我如何靠注射器取一定量的样品？

Solutions:

解决办法：

• Weigh an empty syringe, fill the syringe (start by assuming the density is 1g/mL), and weigh again. Adjust until the weight is accurate. opriate division

• 称量一个干净的注射器，将注射器充满（假设密度为1mg/ml），然后再次称量。调整直至重量精确，在

• For small amounts of viscous liquids, weigh an empty pipette, dip the tip in the substance, and weigh again.

对于少量的有粘度的液体，称量一个干净的移液管，蘸以下，再称量一次。



Problem: When I try to use a syringe to measure a certain liquid, nothing happens because it is too viscous to be drawn into the syringe.

问题：我想用注射器称量一种液体，由于液体太粘稠无法吸取至注射器内。

Solutions:

解决办法：

• Dilute the liquid with your reaction solvent, and then try using a syringe.

• 稀释至反应溶剂中，再试试。

• For small amounts of viscous liquids, weigh an empty pipette, dip the tip in the substance, and weigh again.

对于少量的粘稠液体，称量一个干净的移液管，蘸一下，再称。



Problem: I have a small amount of an oil (say, 40 mg) in a flask. I only want to use some of it (say 10 mg), but I do not know how to weigh it accurately.

问题：现有少量的一种油状物（比如说40mg）至烧杯中，我只需要其中一部分（比如说10mg），但是我不知道如何精确称量。

Solution: For the example given, dissolve the material in 4 mL of solvent, and remove 1 mL. You can remove the solvent to check the weight. This method is more accurate than you might think.

正如例子所说，将该物质溶于4ml溶剂中，然后取1ml。可以采样称量的方法确定重量。该方法更加精确。

Problem: I want to weigh a hygroscopic solid, but it "melts" as I weigh it, and then I can not easily tranfer it to my reaction.

问题：我需要称量一种易吸湿的固体，但当我称量时它处于融化状态，称量后无法转移至反应液中。

Solutions:

解决办法：

• Weigh the reagent in a glove box, if one is available.

• 称量该试剂于手套式干燥箱中，如果该干燥箱易得。

• Weigh the reagent directly into your reaction flask, if practical.

• 称量该试剂直接加入反应瓶中，如果操作可行。

• Weigh the reagent in a glass vessel, and then dissolve it in an appropriate solvent for transfer.

称量该试剂于玻璃试管中，然后用适当的溶剂溶解，再转移。



Problem: I want to weigh a reagent with a melting point near room temperature. It keeps changing states on me- it clogs a syringe, but melts on weighing paper! (t-BuOH is one example).

问题：我想称量一种试剂，它熔点接近室温。它总是变换形态---在注射器中易堵，在称量纸上易溶（如正丁醇）



Solution: Warm it up slightly (if it is heat- stable) and syringe quickly, before it cools enough to solidify.



解决办法：稍微升温（如果对温度稳定）然后用注射器快速称量，在它降温之前。

Problem: I want to syringe a liquid that evaporates at room temperature, and I never get an accurate volume.

问题：我需要抽取一种液体在室温蒸发，但我没找到一种精确的体积。

Solution: Cool it to a low temperature before syringing it.

解决办法：抽取之前降温处理。