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电解法制备银粉 – 译学馆
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电解法制备银粉

Make Silver Powder by Electrochemistry

Greetings fellow nerds.
朋友们大家好
So i needed to make silver powder.
我需要制作一些银粉
I can use bulk silver coins for my reactions
我可以选择大量银质硬币来实现这个化学反应
but powder is far easier to measure and reacts much faster due to greater surface area.
但是粉末更容易测量 而且因为表面积更大反应也更快
Now I could have simply ground down my coins using a file or mechanized grinder
我原本可以用一个锉刀或者电动粉碎机来粉碎硬币
and while that would have worked very well
虽然那两种方法制银粉效果会非常好
i wanted to try an alternative electrochemical approach.
但我还是想尝试另一种电化学方法
Granted it’s rather slow but very interesting, at least to me anyway.
电化学方法虽然相当慢 但至少对我来说它很有趣
In my first attempt I had a solution of 50mL water with 1g of silver nitrate.
在第一次实验中 我在烧杯里放了50毫升的水和1克硝酸银
In it I placed a silver coin and a carbon rod.
然后我在溶液中放入了一枚银币和一根碳棒
The silver was connected to the positive terminal of my power supply making it the anode
银币和我的电源的正极端相连接 为阳极
and the carbon rod was connected to the negative terminal making it the cathode.
碳棒连接电源的负极端 为阴极
Turning on the power, i dialed up the current
我打开电源开关 缓慢加大电流
until the carbon rod just started to bubble hydrogen gas
直到碳棒上开始冒出氢气
and then dialed back about 25%.
然后将电流减小大约25%
Now the silver is being electrochemically oxidized at the anode into silver ions.
现在银单质在正极被电化学氧化成银离子
The dissolution isn’t perfectly even though so
尽管如此 这种溶解方法并不完美
particles of silver metal actually exfoliate off and fall to the bottom as you can see here.
如你所能观察到的那样 一部分银金属颗粒脱落并掉到了瓶底
This is a rather crude way of making silver powder but it works.
虽然这种制银粉的方法很粗糙 但行之有效
Meanwhile, the silver ions that did dissolve migrate over to the cathode
与此同时 溶解的银离子向阴极移动
where they get reduced back into silver metal.
在阴极 这些银离子被还原成银单质
The interesting thing about this process is that
在这个过程中有趣的是
the silver doesn’t deposit as a continuous layer of bulk metal, but rather as individual crystals.
银没有沉积成块体金属中一个连续的层状 而是以单晶的形式沉积
You actually saw me exploit this years ago when i filmed electrochemical crystal growth under a microscope.
你或许看过我多年前使用这样的方法 当时 我在显微镜下拍摄电化学的晶体生长过程
Now if we use a high current density like we are here
现在假如我们选择一个高电流密度 就像我们现在做的这样
then the solution right next to the silver depletes pretty quickly,
那么银单质周围的溶液就会快速大量减少
so the growth is limited by diffusion of the ions.
晶体生长就会受限于离子的扩散
Since diffusion is random,
因为离子的扩散是随机的
the crystals constantly nucleate at new sites
晶体不断地在新的位置成核
and this in turn forms numerous weak crystals that easily crumble into a powder.
这样继而形成了无数易碎成粉末的弱的晶体
And that is exactly what we’re looking for in making electrolytic powdered silver.
在利用电解法制备银粉中 这种脆弱的晶体正是我们想要的
Unfortunately, as you can see, we’re running into a rather annoying issue.
不幸的是 如你所见 我们遇到了一个相当烦人的问题
The silver is growing toward the anode.
银单质正在阳极附近生成
This is because the electric field in the solution favors deposits of silver closer to the anode
这是因为溶液中的电场有利于银沉积在阳极附近
as that has the least electrical resistance.
因为那样的情况电阻最小
And as this occurs it forms dendrites that quickly travel over and contact the anode.
这种情况下 银形成枝晶 这些晶体快速转移并接触阳极
This is undesirable because when this happens the cell shorts out
然而这并不是我们想要的 因为这种情况下电池就会短路
and we’re unable to deposit more silver as all the current is now going through the connection rather than the solution
我们不能沉积更多银单质 因为电流现在只从短路的连接处经过而非经过溶液
We’re going to need to be a little more creative in making our silver powder.
我们需要更具创造性地来制备银粉
Now because the silver is very weakly connected and easily crumbles,
因为银(与电极)之间的连接很弱且易碎
just some mechanical knocking will dislodge the silver connection
一些机械碰撞就能破环银的连接处
So I just put in a stir bar to constantly knock the anode, and it actually worked pretty well.
所以我只需要放进一个搅拌棒去不停地敲打阳极 事实证明这样很有效
The silver connections that did formed were constantly knocked off the anode and settled onto the bottom.
原来附着在阳极上的银被不断地敲下来落到瓶底
That’s not the best solution.
然而这并不是最好的解决方法
The silver anode itself is dissolving, since that’s our intention when converting it into silver powder,
因为把阳极的银币转换成银粉是我们的目的 所以阳极在溶解
so as it dissolved it eventually became too small to be hit by the stir bar.
所以溶解的过程中 搅拌棒就会因为阳极体积变小而敲打不到它
Eventually the silver connected again and shorted out the cell.
最终银单质再一次连接阴阳两极 使电池短路
Fixing that was simple enough.
但解决这个问题再简单不过了
Just arrange the electrodes so that the cathode is constantly struck by the stir bar.
调整一下电极 让搅拌棒可以持续敲打到阴极就行了
And now we have a viable electrolytic silver powder making cell.
现在 我们就有了一个有用的电解法制银粉的电池
The silver constantly deposits onto the cathode
银单质不断沉淀在阴极上
but the continual striking of the stir bar knocks off the deposit
但搅拌棒也在不停地把沉淀从阴极敲打下来
and allows this to continuously produce silver powder until the anode runs out.
从而促使银沉淀不断地产生银粉 直到浸入溶液中的阳极溶解殆尽
At which point we submerge more of the anode to continue.
这时我们就把剩余的阳极浸没在溶液中继续产生银沉淀
But eventually the best arrangement I found was to very carefully place the cathode just above the stir bar.
但最终我找到的最好的方法就是把阴极紧挨着放在搅拌棒的上方
As the silver dendrites grow out they sag into the stir bar and get shredded by it.
树突状银沉淀一生成就会下垂到搅拌棒所在的部位 然后被搅碎
For now i’m not removing the collected silver powder,
现在我不会把累积的银粉拿出
but if it becomes excessive that it contacts both electrodes despite the stir bar
但如果银粉过多以至于即使有搅拌棒 它还是会连接阴阳两电极
then you should filter it out before continuing
那么你就应该它过滤出来 然后继续
At this point I should mention that if you have a physically large cell,
此时此刻我应该提醒一下 如果你有一个体积很大的电池
like more than ten centimeters distance between electrodes,
比如在两个电极之间有十厘米那么远
just the weight of the silver is usually enough to cause it to break off as it runs.
仅仅银粉本身的重量就足够折断其在阴阳两极之间的连接
That is actually how it’s done on large scale silver refining.
这就是大规模提纯银的方法
So all this messing around with knocking electrodes is moot.
所以这里敲打电极 一片狼藉 其实是毫无意义的
But if you’re working on a very small scale like I am,
但如果你像我一样制作银粉的规模很小
then you have to worry about the deposited silver bridging the electrodes
那么你就必须考虑银沉淀会连接两电极的问题了
Anyway, there is the last chunk of silver.
无论如何 只剩最后一小块银币了
I can’t submerge it further without also submerging the power clip.
我如果让剩下的银币浸在溶液中 那么电夹也必会浸入
And i don’t want that because i don’t want to dissolve the steel in it and contaminate my silver.
这样就会使钢溶解从而使制出来的银粉不纯
So i’m going to stop here.
所以我选择此时停止反应
And there is our electrolytically formed silver powder.
看 这就是我们电解法所制得的银粉
Now i decant off the supernatant and wash the silver a few times with water.
然后轻轻倒出上层清液并用水洗涤银粉数次
Then i dry it on the hotplate.
然后用电炉干燥银粉
And there it is, silver powder.
看 这就是制出的银粉
Sure I could have simply filed down my silver coin
确实 我本可以很简单地碾碎银币得到银粉
but this was a lot more fun if a lot slower and labor intensive
虽然需更多时间和细致的工作 但电解法更有趣
I’m going to use this silver to try and make batteries.
这些银粉将被用来制作电池
And the leftover chunk of silver metal i’ll probably keep for other experiments that need silver.
而且我也会保留这个银块用于其他需要银的实验
Thanks for watching.
感谢观看
Special thank you to all of my supporters on Patreon
特别感谢我在众筹网上的所有支持者
for making these science videos possible with their donations and their direction.
通过捐赠和建议让这些科学视频能够面世
If you are not currently a patron, but like to support the continued production of science videos like this one,
如果你现在还不是资助人 但希望支持像此视频一样的科学类视频的制作
then check out my patreon page here or in the video description.
那么就来屏幕下方或视频简介中我的众筹网页看看吧
I really appreciate any and all support.
真挚地感谢所有的支持

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视频来源

https://www.youtube.com/watch?v=WRgSviGuEFY

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