Sciencemadness Discussion Board - lead nitrate synthesis

lead nitrate synthesis

menchaca - 13-3-2003 at 05:12

well im not sure if it works because i have never try it but maibe it works... i need your help to know if this can work or if doesen´t.
All you will need is:

a piece of lead
sulphur
hidrochloric acid
sodium or potasium nitrate
sodium hidroxide
NaHSO4(i dont know how does it write in english)

well reaction is quite simple i thing:

Pb+S --> PbS

PbS + 2HCl --> PbCl2 +H2S(gas.)

PbCl2 + 2NaOH --> NaCl + Pb(OH)2 with precipitates

Pb(OH)2 + 2NaOH --> Na2PbO2 + 2H2O

Edit by chemoleo: changed terrible spelling.

[Edited on 28-3-2005 by chemoleo]

BASF - 14-3-2003 at 12:26

Pb+S --> PbS

Melted lead + slow addition of sulfur under absence of air? - i never tried that...
PbS is identical with the natural mineral "lead glance" also called "galena"

PbS + 2HCl --> PbCl2 +H2S(gas.)

This works!-H2S is highly toxic!!!-Beware.

PbCl2 + 2NaOH --> NaCl + Pb(OH)2

Lead chloride is insoluble in cold water, but soluble in hot water.
I think the pricipitation of Pb(OH)2 is also possible with Na2CO3(Pb(OH)2 has a lower solubility than PbCO3, which would have the advantage not to redissolve lead by taking too much NaOH...).

Pb(OH)2 + 2NaOH --> Na2PbO2 + 2H2O

This also works, you can redissolve precipitated Pb(OH)2 with excess NaOH.....but what do you intend with that??

[Edited on 15-3-2003 by BASF]

BASF - 14-3-2003 at 13:00

What about that(i have tried that already

):

Lead metal + NaHSO4 + KNO3 + gentle heating and evolution of NOx.

Use a wide glass container.
The result is a mix of KNaSO4, Pb(NO3)2 and eventually rests of the reactants.

It is difficult to seperate the lead nitrate form the alkali sulfates, but maybe multiple recrystallization can do it.

Another idea i had would be to precipitate the sulfate with CaCl2 with better chances to seperate the salt-mix then, because NaCl forms and this has a constant solubility at all temperatures, as opposed to Na2SO4, for example.

P.S.:
Keep in mind that Pb(NO3)2 is a mutagenic substance, don´t touch with fingers as it can be absorbed through the skin!

LUEshi is my god - 27-3-2005 at 18:17

This is a rather old topic, but since it pertains to the subject at hand (sort of)...

Can't one produce lead nitrate like this?

CuSO4 + 2NaOH -> Na2SO4 + Cu(OH)2 [One product is soluble, the other is not. Fairly pure Cu(OH)2 can be had]

Cu(OH)2 + 2NH4NO3 -> Cu(NO3)2 + NH3 [One product is a gas. Fairly pure Cu(NO3)2 is formed]

Cu(NO3)2 + Pb -> Pb(NO3)2 + Cu [It works with copper acetate, so should for the nitrate as well, no?]

With lead, ammonium nitrate, copper sulfate, and sodium hydroxide being availible OTC in root killer, fishing sinkers, drain opener,and cold packs (Obviously not in that order), that seems to be the easiest route to lead nitrate, even if it's not the fastest.

[Edited on 28-3-2005 by LUEshi is my god]

darkflame89 - 28-3-2005 at 01:22

hmm..another method posted before is this:
mix lead(II) carbonate with ammonium nitrate and heat. lead(II) nitrate should be formed as well as ammonia(escapes) and carbon dioxide(escapes).

Taaie-Neuskoek - 28-3-2005 at 04:03

Cut lead in small chunks, or grind it to coarse powder, and add 30% HNO3... heat and stir for a few hours, untill most of the lead is dissolved. Decant the liquid (is very easy due to the high desity of lead), and evaporate until dryness. Redissolve in dH2O, and evaporate again, to remove the rest of the acid.

SAM4CH - 6-4-2005 at 04:24

Can I make lead nitrate from 60%HNO3 + Lead metal by elecrtolysis (lead is anode).

Esplosivo - 6-4-2005 at 07:50

You don't need electrolysis, simply place the metal in the acid. Dilute the acid a bit, at least add 1/4 it's volume of distilled water. Add an excess of Pb filings and decant when effervescence stops. The soln contains lead (II) nitrate. Evaporate off the water till crystallization occurs, viola.

Edit: For Christ's sake, look at the post above yours next time!!! This doesn't even need the use of a search engine man!

[Edited on 6-4-2005 by Esplosivo]

hodges - 6-4-2005 at 17:13

Assuming an excess of nitric acid was used, would the remaining liquid still evaporate? I once tried to make copper sulfate by dissolving a copper penny in dilute H2SO4 + H2O2. The liquid would never evaporate to give me the copper sulfate. I ended up having to neutralize it with a base, wash the copper hydroxide, and then carefully add just enough H2SO4 to again dissolve the copper hydroxide again. Does this problem not occur when using nitric acid to make nitrates? What about when making chlorides with HCl?

neutrino - 6-4-2005 at 17:43

It sounds to me that you had extra sulfuric acid present. It being a nonvolatile acid, it wouldn't have evaporated easily. Nitric and hydrochloric acids, however, are volatile, so you shouldn't get this problem.

Theoretic - 7-4-2005 at 09:40

Dropping pieces of lead into molten ammonium nitrate should work, first lead is oxidized by the nitrate ion to PbO, then the nitrite reacts to nitrogen and water with the ammonium, then the ammonium reacts with PbO to produce lead nitrate, ammonia gas and water vapour. Or, if you're paranoid about AN sensitizing due ta lead nitrate, add AN bit by bit into molten lead nitrate.

hodges - 16-4-2005 at 14:25

I just finished making some lead nitrate from lead metal and HNO3. I used 2.1g of Pb metal and 70% HNO3 diluted about 1:1 with water. After letting the liquid evaporate (took several times longer than water would to evaporate), I ended up with a bunch of small square crystals that look almost exactly like table salt. The yield was 3.2g (theoretical is 3.35).

A couple of notes. It took a long time for the lead metal to dissolve in the HNO3. I found it helped quite a bit to immerse the test tube I used for the reaction in hot water. Quite a bit of gas (NO and NO2) is evolved - the lead bubbles vigorously for a long time. I put a wet paper towel over the test tube and this did a very good job of getting rid of the fumes. In fact, I didn't smell anything until I took away the paper towel. The paper towel did become saturated with HNO3 though, and turned my fingers yellow where I picked it up.

It took a couple of hours for the Pb metal to dissolve completely (even with the hot water) and a couple weeks for the remaining HNO3 to evaporate.

I tested my Pb(NO3)2 by making a couple drops of solution of it in water on a paper towel and verified that the wet part of the paper towel turned black when I exposed it to H2S.

Hey there

chloric1 - 17-4-2005 at 07:52

Most of the proceedures discussed here seem workable but I have a much safer and easier method in mind. Espeically if you have lead that has antimony alloyed with it it may not want to dissolve in HNO3 too well. Mixed glacial acetic acid with 30% H202 and you will have lead acetate in solution. Take this and precipitate lead carbonate then add dilute HNO3 until gas evolution stops. No hot concetrated acids or deadl NOx fumes here. Not to mention the insidious H2S formed from handling sulfides with acid.

[Edited on 4/17/2005 by chloric1]

Quince - 18-4-2005 at 22:16

Well, that's good if one can obtain glacial acetic acid...

Is boiling off the liquid instead of slowly evaporating a problem in the HNO3 method?

[Edited on 19-4-2005 by Quince]

Blackout - 2-5-2005 at 13:23

hey, look here:
Pb3O4 + 4 HNO3 ---> 2 Pb(NO3)2 + PbO2 + 2 H2O

Pb3O4 is a brown-red powder that can be found in paint store as an anti-rust for iron enclose
HNO3, well...

12AX7 - 2-5-2005 at 17:21

The way I see it, if you got nitric just use plain lead metal and let the hydrogen rip... why pay someone for oxides.

Tim

Blackout - 2-5-2005 at 18:12

the precipited PbO2 can be filtred out and reacted with conc. H2SO4 and MnSO4 to form HMnO4 then precipitate out KMnO4 by the addition of a conc. solution of KCl to the diluted acid...

neutrino - 2-5-2005 at 18:46

Quote:

Originally posted by 12AX7
The way I see it, if you got nitric just use plain lead metal and let the hydrogen rip... why pay someone for oxides.

Nitric acid + lead gives you water, lead nitrate, and NOx, not lead nitrate and hydrogen. You’d be loosing a good deal of your acid as nitrogen oxides here.

12AX7 - 2-5-2005 at 21:01

Right, it hates people and gives NO2 with less reactive metals...

Tim

TheBear - 30-5-2005 at 11:57

Another cheap way of making it would be by making an separated cell (saltbridge) and electrolyse with KNO3/NaNO3. Use Pb as anode, cathode can be made of any resistant material. The same works for making AgNO3. Think I read this in another thread.

But now I have a question. With nitric acid I believe the redox works like this:

The nitrate ion is reduced:

NO3- + 2H+ + e- ---> NO2 + H2O

Or with lower pH:

NO3- + 4H+ + 3e- ---> NO + 2H2O

And lead being oxidized:

Pb ---> Pb2+ + 2e-

I believe it goes like that, but what I can't figure out is how it looks in the cell. What do the anode reaction look like? Will NOx-gases form then aswell?

Quince - 30-5-2005 at 14:05

Nitric in both half-cells?

[Edited on 30-5-2005 by Quince]

Jome - 31-5-2005 at 11:29

How about simply mixing aquaeus solutions of CuSO4 and Ca(NO3

2 which would precipate CaSO4 (gypsum) and leave Cu(NO3

2 in solution, the latter easily converted to lead nitrate by metallic lead added to soln (PbO might work too).

Ca(NO3

2 is found naturally occuring in 10kg bags in garden shops, "chalk salpetre".

Esplosivo - 31-5-2005 at 12:07

Yes, it can be done that way. The CaSO4 has a low solubility in water, so I guess it can be filtered out quite easily.

Lol I liked this:

Quote:

Ca(NO3)2 is found naturally occuring in 10kg bags in garden shops, "chalk salpetre".

neutrino - 31-5-2005 at 13:07

No, I can assure you that will not work. The CaSO4 precipitate is extremely difficult to filter out, if not impossible. More than one person on this board has tried something like this and utterly failed. It’s like trying to filter the water out of mud, IIRC.

chemoleo - 31-5-2005 at 13:14

Errr.... neutrino, I wrote a big post(s) about this once, and I can personally vouch for it that it works VERY nicely.
Unless you think making more than 1 kg of lead acetate from calcium acetate, CuSO4 and lead metal is a failure

Anyway, using calcium nitrate instead of the acetate works of course too. Just be patient when filtering, and best is to mix the nitrate with the copper sulphate, and pour this onto a coffee filter. Compress the CaSO4 now and then, using a spoon. Once everything is filtered, you can wash it with H2O to extract more of the Cu nitrate. You won't get the CaSO4 completely white however, as I believe some mixed crystals are formed. Regardless this procedure works very well, the only true patience that is required is to react the Cu(NO3)2 with the Pb.

Once the reaction is done, the solution is completely clear. It might take a couple of weeks or longer depending on the surface area of the lead/stirring/temp etc.

Then you could evaporate the solution to isolate the leadnitrate by crystallisation, add Ethanol, or whatever suits you.

[Edited on 31-5-2005 by chemoleo]

Jome - 31-5-2005 at 13:45

Are you saying Lead nitrate be isolated in the same way as KNO3, by addition of ice cold ethanol? Is this method as efficent with lead nitrate?

I've had a solution of it sitting for months in a huge jar, being to scared of droplets and such to appempt boiling it down.

chemoleo - 31-5-2005 at 14:21

Well I don't know, but I suspect that lead nitrate being an ionic salt it won't be well soluble in ethanol, thus it should precipitate. I haven't tried that though, I used crystallisation and evaporation.

Try it and see if it works. I should think it will.
Else, try acetone, which is slightly better for precipitation (albeit more expensive).

neutrino - 31-5-2005 at 15:15

I was going by personal experience and others’ posts. I had never come across any testimony to its actually working. Thanks for enlightening me.

chemoleo - 31-5-2005 at 15:29

Quote:

The CaSO4 precipitate is extremely difficult to filter out, if not impossible. More than one person on this board has tried something like this and utterly failed.

I wonder who those people are. I remember marvin commenting elsewhere this being difficult, I think over at the E&W where I first described it, and I remember telling him it is absolutely doable. And I made 10 litres (!) of Cu acetate solution that way!

I presume the problem was that when people attempted it that they used too little water vs Caacetate/nitrate and thus got those problems.
And for this reaction, concentration doesn't really matter that much as the equilibrium of Pb dissolution lies very far to the right.

neutrino - 31-5-2005 at 15:34

Ah, that might have been my problem: not enough water. I can't remember exactly who the other person was...

Jettin4u - 1-7-2005 at 08:45

I have made lead nitrate by using lead oxide and nitric acid, you could also use lead carbonate and nitric acid. just filter, boil down and recrystalize
But im not sure what you guys can get your hands on though. This is the easiest way.

chloric1 - 16-11-2005 at 21:39

I guess in the past I must have had antimonial lead as I could not get it to dissolve in nitric acid too well. The lead sheet I have from Mcmaster Carr that I bought for aluminum anodizing is quite pure. In a 1:1 ratio of nitric acid to water by volume you can get a decent sized 35 gram strip to dissolve in 2.5 hours. I applied moderate heat. Chemical action was seen at about 42 to 44 degrees C but was lethargically slow. Above 60 it was more steady by the time the solution reached the high 80's most of the lead is almost gone. Lead nitrate not being soluble in nitric acid is a strong plus indeed. I simply decant the liquid and reuse with more lead and add nitric acid an water as needed. That way I am never losing nitric acid except towards evaporation.

[Edited on 11/17/2005 by chloric1]

Lead Monoxide

ADP - 22-11-2005 at 17:07

Is there an easy route to produce lead monoxide? I didn't think this question warranted a new thread.

stygian - 22-11-2005 at 17:17

I don't think it even warrants a post. Try searching.

Pure Lead nitrate!

SAM4CH - 9-5-2006 at 01:25

I have technical lead alloy "about 90% Lead" and I want to make pure lead nitrate "I have very good method for that" but I like to purify lead alloy to be around 98-99% and I do not know the composition of the other material in this alloy.

I tryed to recrystalize my lead nitrate but it was not good idea.!!

12AX7 - 9-5-2006 at 10:12

Hum, electroplate it?

Tim

unionised - 9-5-2006 at 12:20

Disolve it in nitric acid, ppt the Pb as PbCl2 with HCl, filter, wash, boil with Na2CO3 to get PbCO3. Filter + wash. Disolve in HNO3.
Since almost all chlorides are soluble this should get rid of everything apart from Ag and Hg (And Tl perhaps- probably not important).
Since Ag and Hg are expensive they probably are not present in the alloy in the first place.
If they are then you could remove them by only disolving 90% of the metal, shredding the rest of it to give lots of surface area and adding this to the solution of Pb(NO3)2. Then Ag and Hg would ppt out as the metals.
Of course, if you actually do this be careful with the NOx fumes when you disolve the metal.

SAM4CH - 7-6-2006 at 03:54

I like to make purification of lead alloy by electrolysis at high current density "I do not like fine electroplate", What the the best electrolyte solution for this?

[Edited on 8-6-2006 by SAM4CH]

SAM4CH - 9-6-2006 at 10:36

[Edited on 9-6-2006 by SAM4CH]

What is the white stuff?

alancj - 16-6-2006 at 03:20

Quote:

Originally posted by TheBear
Another cheap way of making it would be by making an separated cell (saltbridge) and electrolyse with KNO3/NaNO3. Use Pb as anode, cathode can be made of any resistant material. The same works for making AgNO3. Think I read this in another thread.

I'm trying this procedure right now; using a lead anode and stainless cathode with potassium nitrate in the solution. I forgot about the salt bridge, and just put the whole of it in a glass jar. It is still running but it appears that I'm getting lead plated on the cathode and I'm getting LOTS of white precipitate forming on the lead anode. It has already settled at the bottom and is about a half inch thick, and it has only been going for an hour. Anyone know what this per. is? I don't have a salt bridge so it could be some other compound. Please enlighten me...

Thanks,
Alan

TheBear - 16-6-2006 at 06:38

At the cathode the following reduction is taking place:

K+ + e- ---> K

Potassium / sodium instantly reacts with water to give off hydrogen gas and hydroxide ions:

4K + 2H2O ---> H2 + 2K+ + 2OH-

And at the anode lead is being oxidised:

Pb ---> Pb2+ + 2e-

Since the cell isn't separated lead will plated on the cathode, and mix with the hydroxide ions resulting in a precipitate consisting of Pb(OH)2.

Pb2+ (aq) + OH- (aq) -----> Pb(OH)2 (s)

So if a soluble lead salt is all you're after just let i run until the lead anode is dissolved (add more electrolyte if needed) and then filter your white precipitate. Then add this to acetic acid and recrystallize the formed lead acetate, Pb(CH3COO)2. (Even though this topic is about making the nitrate, I assume you're not in possession of nitric acid, or if you are, use it instead to form the nitrate).

alancj - 16-6-2006 at 13:48

Quote:

Originally posted by TheBear
At the cathode the following reduction is taking place:

K+ + e- ---> K

Potassium / sodium instantly reacts with water to give off hydrogen gas and hydroxide ions:

4K + 2H2O ---> H2 + 2K+ + 2OH-

And at the anode lead is being oxidised:

Pb ---> Pb2+ + 2e-

Since the cell isn't separated lead will plated on the cathode, and mix with the hydroxide ions resulting in a precipitate consisting of Pb(OH)2.

Pb2+ (aq) + OH- (aq) -----> Pb(OH)2 (s)

So if a soluble lead salt is all you're after just let i run until the lead anode is dissolved (add more electrolyte if needed) and then filter your white precipitate. Then add this to acetic acid and recrystallize the formed lead acetate, Pb(CH3COO)2. (Even though this topic is about making the nitrate, I assume you're not in possession of nitric acid, or if you are, use it instead to form the nitrate).

I thought maybe i would get hydroxide. Wasn't sure. What happens to the NO3 and K ions? Do they just float about? Would I be able to make the Pb(OH)2 with a different salt, like NaCl? Also, my solution smells strongly like a ammonia, why is that? I guess ammonia is NH3 so maybe some of the hydrogen is combining with the N in the NO3 and relasing the O3, which would be ozone... I'm just guessing though, I don't know much chemistry, I only took half a year of high school chem

.

-Alan

12AX7 - 16-6-2006 at 13:56

Nah, the O breaks off with hydrogen at the cathode, producing water.

Eh, was afraid of that... I noticed, with a strong chlorate solution (around 50g/100ml NaClO3, I think), weird smells and behavior being produced, my guess is the chlorate ion was being reduced.

Nitrate and chlorate are about on par... they decompose about the same temperature for instance.

Maybe perchlorate is stable enough to provide gobs of easy lead hydroxide?

Any thoughts on preventing the lead sponge deposit at the cathode? I *always* get one. I also get, when the Pb(OH)2 isn't scraped off hourly, a transformation to PbO2, which cakes on and ends up making a mess of things (a hodge-podge of chemistry then going on).

(Hmm this should be moved to the PbO thread...)

Tim

hodges - 16-6-2006 at 14:03

Quote:

Originally posted by alancj
Also, my solution smells strongly like a ammonia, why is that? I guess ammonia is NH3 so maybe some of the hydrogen is combining with the N in the NO3 and relasing the O3, which would be ozone... I'm just guessing though, I don't know much chemistry, I only took half a year of high school chem

At the cathode (negative terminal), some of the nitrate ion from the KNO3 is getting reduced to ammonium ion. Since the solution is basic at the cathode, the ammonium ion is forming ammonium hydroxide which you smell.

alancj - 16-6-2006 at 14:59

Quote:

Originally posted by 12AX7
Nah, the O breaks off with hydrogen at the cathode, producing water.

Eh, was afraid of that... I noticed, with a strong chlorate solution (around 50g/100ml NaClO3, I think), weird smells and behavior being produced, my guess is the chlorate ion was being reduced.

Nitrate and chlorate are about on par... they decompose about the same temperature for instance.

Maybe perchlorate is stable enough to provide gobs of easy lead hydroxide?

Any thoughts on preventing the lead sponge deposit at the cathode? I *always* get one. I also get, when the Pb(OH)2 isn't scraped off hourly, a transformation to PbO2, which cakes on and ends up making a mess of things (a hodge-podge of chemistry then going on).

(Hmm this should be moved to the PbO thread...)

Tim

I didn’t measure the amounts put into the cell, but I estimate I had 500 ml of tape water and I added 4 spoonfuls of KNO3… So maybe 50 grams. It all dissolved in the water cold.

Perchlorate… that’s funny, you need perchlorate to make lead salts to make lead dioxide anode to make perchlorate.

Well, since some lead is plated and some turns into hydroxide…maybe having both electrodes being lead and then reversing the current every few seconds would cause all the lead to eventually turn into hydroxide. It could be done with some pretty simple electronics, probably just some relays and 555 timer.

Quote:

Originally posted by hodges

Quote:

I read that ammonium hydroxide is just aqueous ammonia, And according to the lead salts table I got from another thread on this board Pb(OH)2 seems to be insoluble. Just 0.00012 g/100 ml at 20 deg Celsius. The next column is “Qualitative Solubility” and it says “s acid” which means it is soluble in acid. So washing the perc. would probably remove the ammonia and then I can dissolve the Pb(OH)2 in vinegar. I only have 5% stuff, but I suppose it would work.

I’m distilling nitric acid right now as well as precipitating my lead chloride that I’ve been making in boiling HCl for the past 2 days. Getting lots of needlely crystals! I wonder what would happen when one does electrolysis with a lead anode in a solution of PbCl2? Not real soluble so it might not be very conductive.

-Alan

12AX7 - 16-6-2006 at 15:55

Quote:

Originally posted by alancj
...as well as precipitating my lead chloride that I’ve been making in boiling HCl for the past 2 days. Getting lots of needlely crystals!

Yep, I've got a jug of impure PbCl2 (among probably clay, rust, etc.) with hot water on top, hotter on the side piled up with PbCl2. Not much has crystallized on the cooler side yet, but it's getting there. More seems to come out due to evaporation loss (which is condensed, but drips back in and doesn't dissolve the crystal mat). *shrug*

Quote:

I wonder what would happen when one does electrolysis with a lead anode in a solution of PbCl2? Not real soluble so it might not be very conductive.

I tried something like that before and posted in the PbO(2?) thread. When warm, in NaCl solution, Pb(OH)2 is produced, because the PbCl2 intermediate is soluble -- same process as you tried, with Na and Cl spectator ions. When cold, PbCl2 precipitates at the anode (along with Pb(OH)2), which is slowly oxidized to a porous, resistive layer of PbO2.

In case you're wondering, sulfuric acid produces a much better PbO2 deposit, which isn't saying much.

Tim

Some experiments with a diaphragm

alancj - 18-6-2006 at 23:42

I made a diaphragm to isolate my SS cathode from the rest of the cell. It sits in an acrylic pocket with six 1/2" holes drilled in one side and uses two layers of filter paper to form a diaphragm. Water and electricity must pass through the paper before it reaches the cathode. It completely stopped the plating of lead onto the SS and instead the spongy lead would build up around the holes in the acrylic where the paper blocks further progress. The lead falls off or is easily scraped off.

Unfortunately I still smelled a strong ammonia odor coming from the cell. And I still get a white insoluble precipitate forming in the cell which I assume is lead hydroxide. The water will also make your fingers very slippery, much like sodium hydroxide does. Lead nitrate, which I'm aiming for, would be soluble and wouldn't precipitate right away.

I thought that a diaphragm would be equivalent to a separated cell with a salt bridge in that they both would stop the transfer of ions. Assuming that two separate containers with a salt bridge would actually work for making lead nitrate, then maybe my diaphragm is not working the way it should. The paper is very close to the cathode, and the hydrogen bubbles certainly come into contact with the paper. I think that that could be the problem. But I don't really know. I could make it a lot more rummy with some modifications if need be.

So, how exactly does a separated salt bridge work for making AgNO3? How is the bridge constructed? What salt is used in the bridge, what is the catholyte and anolyte? All the same? Would a diaphragm work to separate the anode and cathode, and if so what's wrong with mine?

Thanks,
Alan

12AX7 - 19-6-2006 at 13:11

Might just need to run it for longer. As long as there are potassium ions in the anolyte, it's probably going to make hydroxide. Wait, that doesn't make much sense, cations spectate at the anode.

Tim

Lead Nitrate

MadHatter - 20-6-2006 at 04:41

The CuSO4/Ca(NO3)2 method works very nicely. Just use some lead filings or #9 lead bird
shot to increase the surface area.