# Separating brass **URL:** \ **Category:** Factual Questions\ **Created:** [March 20, 2006, 2:10am UTC](https://boards.straightdope.com/t/separating-brass/349075 "2006-03-20T02:10:20Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [March 20, 2006, 2:10am UTC](https://boards.straightdope.com/t/separating-brass/349075/1 "2006-03-20T02:10:20Z")
Brass is a solid solution of copper and zinc. Is there an easy way to take scrap brass metal, and separate it back into copper and zinc? Arjuna34 ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [March 20, 2006, 3:04am UTC](https://boards.straightdope.com/t/separating-brass/349075/2 "2006-03-20T03:04:36Z")
Get it hot enough to boil away, and then condense the gas. Copper and zinc condense at different temps, so they will separate out. That’s simple, but not necessarily easy. Just getting brass hot enought to boil may be difficult. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [March 20, 2006, 3:08am UTC](https://boards.straightdope.com/t/separating-brass/349075/3 "2006-03-20T03:08:41Z")
> [@Arjuna34](#): > > Brass is a solid solution of copper and zinc. Is there an easy way to take scrap brass metal, and separate it back into copper and zinc? > > Arjuna34 See [Brass recycling](http://www.brass.org/recyclin.htm) Brass is considerably more valuable recycled as brass than separated into its separate copper & zinc components. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [March 20, 2006, 3:11am UTC](https://boards.straightdope.com/t/separating-brass/349075/4 "2006-03-20T03:11:43Z")
> [@t-bonham@scc.net](#): > > Get it hot enough to boil away, and then condense the gas. Copper and zinc condense at different temps, so they will separate out. > > That’s simple, but not necessarily easy. Just getting brass hot enought to boil may be difficult. Holy Mackerel. A distillery. ---
**Author:** ![Tabby\_Cat](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@Tabby\_Cat](https://boards.straightdope.com/u/Tabby_Cat)\ **Post date:** [March 20, 2006, 3:11am UTC](https://boards.straightdope.com/t/separating-brass/349075/5 "2006-03-20T03:11:51Z")
Apparently, you don’t need to vapourise the alloy, you can simply melt the Zinc out from the Copper, due to the great difference in melting terperatures… [http://www.newton.dep.anl.gov/askasci/chem03/chem03403.htm](http://www.newton.dep.anl.gov/askasci/chem03/chem03403.htm) ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [March 20, 2006, 4:30am UTC](https://boards.straightdope.com/t/separating-brass/349075/6 "2006-03-20T04:30:25Z")
> [@Tabby\_Cat](#): > > Apparently, you don’t need to vapourise the alloy, you can simply melt the Zinc out from the Copper, due to the great difference in melting terperatures… > > [http://www.newton.dep.anl.gov/askasci/chem03/chem03403.htm](http://www.newton.dep.anl.gov/askasci/chem03/chem03403.htm) Here’s a chart that lists melting points for several types of brass: [http://www.engineeringtoolbox.com/melting-temperature-metals-d\_860.html](http://www.engineeringtoolbox.com/melting-temperature-metals-d_860.html) They are higher than the melting point or even the boiling point of zinc (1664 F). What happens if you heat brass up past the melting point of zinc, or even the boiling point? Why would a melting point for brass be listed if it’s no longer brass after that? I think there’s one clue in the brass recycling link **astro** gave: > [@](#): > > When brass is remelted, there is usually some evolution of the more volatile zinc. This is made up in the melt to bring it back within specification. The zinc is evolved as oxide that is drawn off and trapped in a baghouse and recycled for the manufacture of other products. Does the zinc just sort of ooze out? I think page 13 of this PDF (linked to from **Tabby\_Cat** ’s link) [Lecture on Copper](http://www.mmat.ubc.ca/courses/mmat380/lectures/2004/Lecture%2020%20-Copper(Complete).pdf) has the answer with their phase diagram, but it’s been about 18 years since my materials science class, so I’m not too sure what it reveals. Arjuna34 ---
**Author:** ![Tabby\_Cat](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@Tabby\_Cat](https://boards.straightdope.com/u/Tabby_Cat)\ **Post date:** [March 20, 2006, 1:24pm UTC](https://boards.straightdope.com/t/separating-brass/349075/7 "2006-03-20T13:24:11Z")
IIRC, the problem with listing melting (or indeedm boiling) points of mixtures is that you get a whole range of temperatures. Take for example, water. When ice is melting, the temperature is exactly zero. The temperature of the ice will remain at zero until all the ice has turned into water (ideally). For a mixture, however, of say, milk, the milk “ice cube” will start melting at temperature x. But the temperature of the cube will continue rising while it melts, unlike water. ---
**Author:** ![LunaEclipsed](https://avatars.discourse-cdn.com/v4/letter/l/eb8c5e/32.png) [@LunaEclipsed](https://boards.straightdope.com/u/LunaEclipsed)\ **Post date:** [November 8, 2016, 6:23am UTC](https://boards.straightdope.com/t/separating-brass/349075/8 "2016-11-08T06:23:37Z")
> [@Tabby\_Cat](#): > > IIRC, the problem with listing melting (or indeedm boiling) points of mixtures is that you get a whole range of temperatures. > > Take for example, water. When ice is melting, the temperature is exactly zero. The temperature of the ice will remain at zero until all the ice has turned into water (ideally). > > For a mixture, however, of say, milk, the milk “ice cube” will start melting at temperature x. But the temperature of the cube will continue rising while it melts, unlike water. thats the funny thing about water and its phase changes though mainly because of its high specific heat when it melts that liquid pulls off all the heat that was generated to make it melt thus keeping it at 0 degrees celcius just like water never gets hotter than 212 degrees unless you heap on additional pressure against it ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [November 8, 2016, 7:44am UTC](https://boards.straightdope.com/t/separating-brass/349075/9 "2016-11-08T07:44:32Z")
> [@Arjuna34](#): > > Does the zinc just sort of ooze out? No. It fumes out. This is … [not healthy for people](https://en.wikipedia.org/wiki/Metal_fume_fever). Catchy name, though. I’ve worked with molten brass - a fume hood or doing it outdoors is a must. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 8, 2016, 12:47pm UTC](https://boards.straightdope.com/t/separating-brass/349075/10 "2016-11-08T12:47:51Z")
> [@](#): > > Quoth **LunaEclipsed** : > > thats the funny thing about water and its phase changes though mainly because of its high specific heat when it melts that liquid pulls off all the heat that was generated to make it melt thus keeping it at 0 degrees celcius just like water never gets hotter than 212 degrees unless you heap on additional pressure against it No, that’s not a funny thing about water. That’s the way any pure substance behaves when going through a phase change. ---
**Author:** ![Tabby\_Cat](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@Tabby\_Cat](https://boards.straightdope.com/u/Tabby_Cat)\ **Post date:** [November 8, 2016, 12:53pm UTC](https://boards.straightdope.com/t/separating-brass/349075/11 "2016-11-08T12:53:15Z")
Wow 2006 huh. I didn’t even remember that I said this. I’m still pretty sure I got it right though! 😃 ---
**Author:** ![excavating\_for\_a\_mind](https://avatars.discourse-cdn.com/v4/letter/e/e8c25b/32.png) [@excavating\_for\_a\_mind](https://boards.straightdope.com/u/excavating_for_a_mind)\ **Post date:** [November 8, 2016, 2:13pm UTC](https://boards.straightdope.com/t/separating-brass/349075/12 "2016-11-08T14:13:05Z")
> [@Chronos](#): > > > [@LunaEclipsed](#): > > > > thats the funny thing about water and its phase changes though mainly because of its high specific heat when it melts that liquid pulls off all the heat that was generated to make it melt thus keeping it at 0 degrees celcius just like water never gets hotter than 212 degrees unless you heap on additional pressure against it > > No, that’s not a funny thing about water. That’s the way any pure substance behaves when going through a phase change. No, the funny thing about water is that it melts at **exactly** 0 degrees C. I mean, what are the odds? And, our new friend, while digging up zombies, mixes units as well. Getting water above 100 degrees (when you’re talking Celsius) is tough to do without a heap of additional pressure. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [November 8, 2016, 3:03pm UTC](https://boards.straightdope.com/t/separating-brass/349075/13 "2016-11-08T15:03:31Z")
> [@excavating\_for\_a\_mind](#): > > No, the funny thing about water is that it melts at **exactly** 0 degrees C. I mean, what are the odds? … [snip] I must be dense this week … water melting at 4ºC would be hilarious … ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [November 8, 2016, 4:40pm UTC](https://boards.straightdope.com/t/separating-brass/349075/14 "2016-11-08T16:40:13Z")
> [@t-bonham@scc.net](#): > > Get it hot enough to boil away, and then condense the gas. Copper and zinc condense at different temps, so they will separate out. > > That’s simple, but not necessarily easy. Just getting brass hot enought to boil may be difficult. It’s easy enough that nearly anyone learning to braze with an oxy-acetylene torch will do it a number of times before they get the knack.