Making Methylamine 3 Ways
Summary
TLDRThis video script delves into the synthesis of methylamine, a versatile primary amine with applications in various industries. It outlines three distinct methods for producing this regulated chemical: a reaction between pralid and ammonium chloride, the decomposition of hexamine, and a Hoffman rearrangement of acetamide. Each method is detailed with its process, challenges, and yields, providing a comprehensive guide for those interested in the chemistry of methylamine production.
Takeaways
- 🧪 Methylamine is an important chemical with various applications in fields like organic chemistry, pharmaceuticals, and water treatment.
- 🚫 Methylamine is regulated by the US government as a precursor chemical, making it difficult to purchase.
- 🔬 The first method demonstrated is the reaction between pralid and ammonium chloride, which is easy but messy and time-consuming.
- ⏱ The process involves monitoring temperature, distillation, and vacuum filtration to collect the product.
- 🔥 A redox reaction occurs during the synthesis, where water is oxidized and methylamine is reduced.
- 🌡 The reaction temperature is critical, with higher temperatures favoring undesired byproducts like dimethylamine.
- 💧 Distillation is used to remove water and formic acid byproducts, and a vacuum is applied to facilitate this process.
- 💊 The final product, methylamine hydrochloride, is purified through recrystallization and vacuum desiccation.
- 📉 The yield of the first method is reported to be 49.9%, which is considered good but still feels inefficient given the amount of starting materials.
- 🔄 The second method involves the decomposition of hexamine and hydrolysis to form methylamine, yielding higher and cleaner results.
- 🧬 The third method, a Hoffman rearrangement, is the fastest and cleanest but resulted in a low yield due to potential impurities or the need for bromine.
Q & A
What is methylamine and why is it important in organic chemistry?
-Methylamine is the simplest primary amine and is extensively used in organic chemistry due to its pervasive role in the synthesis of various compounds such as accelerants, propellants, pharmaceuticals, insecticides, fungicides, surfactants, fuel additives, polymerization inhibitors, components in paint strippers, solvents, water treatment agents, and photographic developers.
Why is methylamine regulated by the US government?
-Methylamine is regulated as a precursor chemical by the US government due to its potential use in the illicit drug manufacturing process, which makes it difficult to purchase for many individuals.
What are the three methods presented in the script for synthesizing methylamine?
-The three methods presented are: 1) Reaction between pralid and ammonium chloride, 2) Decomposition of hexamine, and 3) Hoffman rearrangement of acetamide.
Why is the first method using pralid and ammonium chloride considered easy but messy?
-The first method is considered easy because it involves straightforward reactants and steps, but it is messy due to the large amount of formalin required, the time-consuming nature of the process, and the difficulty in handling and collecting the product.
What is the role of methanol in the first method of synthesizing methylamine?
-Methanol is used in the first method to stabilize the formalin solution, preventing oxidation or polymerization. It also participates in side reactions forming meth formate and acetyl methylol, which have low boiling points and distill off early in the reaction.
What is the significance of vacuum distillation in the synthesis process?
-Vacuum distillation is significant as it allows for the removal of excess water and byproducts at lower temperatures, preventing the formation of undesired byproducts and facilitating the collection of the desired product, ammonium chloride, for potential reuse.
What is the primary byproduct in the second method using hexamine?
-The primary byproduct in the second method is formic acid, which is formed due to the absence of methanol and the more acidic conditions of the reaction.
How does the Hoffman rearrangement method differ from the first two methods?
-The Hoffman rearrangement method differs as it involves a more complex process starting with acetamide and using an alkaline source of bromine or chlorine, resulting in a series of reactions that yield methylamine. It is also noted for being the fastest and cleanest method, but with potential issues regarding yield and purity.
What is the reason for the low yield in the third method using the Hoffman rearrangement?
-The low yield in the third method could be attributed to the impurity of the acetamide used or the necessity of using bromine instead of hypochlorite for the reaction to be efficient.
What safety precautions are necessary when handling methylamine and its precursors?
-Safety precautions include working under a fume hood to avoid inhaling toxic and foul-smelling gases, using personal protective equipment, and being cautious with exothermic reactions to prevent overheating and potential hazards.
Outlines
🧪 Synthesis of Methylamine: Pralid and Ammonium Chloride Method
This paragraph describes the first method of synthesizing methylamine, a crucial chemical in various industries, using pralid (formalin) and ammonium chloride. The process involves heating these chemicals in a round bottom flask with a distillation setup, monitoring the temperature to ensure the formation of methylamine hydrochloride. The reaction is messy and time-consuming, with a focus on the formation of byproducts like formic acid and methanol. The author also discusses the challenges of obtaining formalin and the legal considerations of producing a regulated chemical. The yield is calculated based on the amount of ammonium chloride used, resulting in a 49.9% yield.
🔬 Methylamine Production via Hexamine Decomposition
The second method for producing methylamine is detailed in this paragraph, which involves the hydrolysis of hexamine using hydrochloric acid. This process is similar to the first but avoids the use of formalin. The reaction is carefully controlled to prevent the formation of unwanted byproducts and to promote the production of methylamine. The author notes the collection of formic acid as a useful byproduct. The yield from this method is higher than the first, with a 72.2% yield, and the author expresses a preference for this method due to its cost-effectiveness and higher yields.
🌡️ Hoffman Rearrangement for Methylamine Synthesis
The third method discussed is the Hoffman rearrangement of acetamide to produce methylamine. This method is noted for being the most interesting, fastest, and cleanest, but it also yields the lowest amount of methylamine due to potential impurities in the acetamide or the necessity of using bromine instead of hypochlorite. The process involves careful temperature control and the addition of reagents to facilitate the rearrangement. Despite the low yield, the author finds this method intriguing and considers retrying it with purer materials.
🛠️ Post-Reaction Processing and Yield Calculation
This paragraph outlines the post-reaction processing steps for the methylamine synthesis, including heating, distillation, and crystallization to purify the product. The author describes the transformation of the reaction mixture into a solution of free base methylamine and the subsequent conversion to methylamine hydrochloride. The yield is calculated, and the author discusses the challenges and potential improvements for the synthesis process, including the possibility of using different reagents or purifying the starting materials more thoroughly.
📢 Conclusion and Call to Action for Viewer Engagement
The final paragraph serves as a conclusion to the video, summarizing the methods and outcomes of the methylamine synthesis and expressing gratitude to patrons for their support. The author encourages viewers to subscribe on various platforms and become patrons for more content, emphasizing the importance of community engagement and the commitment to fulfilling patron requests.
Mindmap
Keywords
💡Methylamine
💡Amine
💡Precursors
💡Formaldehyde
💡Hydrochloride
💡Vacuum Distillation
💡Hexamine
💡Hoffman Rearrangement
💡Yield
💡Recrystallization
💡Hypochlorite
Highlights
Methylamine is the simplest primary amine with extensive uses in organic chemistry, including syntheses of various chemicals and as a fuel additive.
Methylamine is regulated by the US government as a precursor chemical, making it challenging to purchase.
The first method involves a reaction between pralid and ammonium chloride, which is easy but messy and time-consuming.
Formaldehyde is used in the first method, which is not easily accessible for many, highlighting the accessibility challenge.
The formation of the chloride salt of methylamine is described, which is easier to collect than the free base.
A series of reactions are explained, including the direct condensation of formaldehyde and ammonium chloride.
The process involves a redox reaction where water is oxidized by methylamine, which is reduced.
The use of vacuum distillation to remove excess ammonium chloride and other byproducts is detailed.
The purification of methylamine hydrochloride involves dissolving in hot methanol and recrystallization.
The yield and purity of the first method are discussed, with a percent yield calculation provided.
The second method uses hexamine and hydrochloric acid to produce methylamine through hydrolysis.
A key difference in byproduct formation between the first and second methods is highlighted, with formic acid being a notable byproduct in the second method.
The Hoffman rearrangement of acetamide is introduced as the third method for synthesizing methylamine.
The use of calcium hypochlorite instead of bromine in the Hoffman rearrangement is mentioned, with a note on the potential for lower yields.
The process of converting the free base methylamine to its hydrochloride salt for easier handling and analysis is described.
The final yield of the third method is discussed, with a note on the potential reasons for the lower yield.
A summary of the video content, emphasizing the interest and educational value of the synthesis methods presented.
Transcripts
today I'm going to show you three ways
to make the extremely important chemical
methylamine methylamine is the simplest
primary amine and as such its use in
organic chemistry is pervasive for
example methylamine is used extensively
in the synthesis of accelerants
propellants pharmaceutical insecticides
fungicides and surfactants it's also
used as a fuel additive a polymerization
inhibitor a component and paint
strippers a solvent a water treatment
agent and a photographic developer
however like some of the other most
ubiquitous and commonplace lab chemicals
you could imagine methylamine is
regulated by the US government as a
precursor chemical which makes it tough
to purchase for reference here are just
some of the other many commonplace lab
chemicals scheduled as precursors this
video took me months to actually release
because I heard so often that this
chemical was under particular scrutiny
but in reality these chemicals are all
identical in the eyes of the law and
that said you'd have a hard time finding
a video on my channel where I don't use
at least one scheduled precursor so in
the end I decided to just say screw it
and make the list a little longer anyway
the first method I'm going to show today
is the reaction between pralid and
ammonium chloride this route is by far
the easiest but it's very messy timec
consuming and requires a large amount of
formalin which is not an easy chemical
for many people to get to get started I
went ahead and added 125 G of ammonium
chloride and 250 ml of 37% formalin to a
three neck round bottom boiler in flask
I then connected a distillation head to
one of the necks a thermometer to
another and capped the third notice here
that the thermometer is immersed in the
solution as I want to monitor the
temperature of the reaction mixture and
not the vapor temperature I turned my
heating mantle to Max and waited until
the temperature at around 104° C now as
the temperature increases a set of
reactions begin to occur that eventually
result in the formation of the chloride
salt of methylamine which is much easier
to collect in weigh than three Bas
methylamine the first reaction that
occurs is a direct condensation of faldy
and ammonium chloride yielding water
hydrogen chloride and the unsaturated
compound
methylamine this reaction happens
spontaneously near ambient temperatures
but as the temperature increases
methylamine water and another molecule
of faldy react to form methylamine and
formic acid this is technically a redox
reaction where in water is being
oxidized by methylamine which itself is
being reduced in the final reaction step
the free base methylamine generated in
the previous step will react with
hydrogen chloride forming the target
methylamine hydrochloride as for the
reaction byproducts here the formic acid
produced is for the most part oxidized
to carbon dioxide and water as the
reaction mixture heats up however
formalin Solutions are stabilized with
10 to 15% methanol in order to prevent
oxidation or polymerization of the
formaly and some of the formic acid will
react with this methanol forming meth
formate and the acetyl methylol which
both have very low boiling points and
will distill off early in the reaction
anyway once the temperature reaches 104°
C I cut the heat and fiddled with it a
bit until the temperature stabilized
between 100 and 105° Celsius this
temperature is held for about 3 hours
while slowly distilling away water in
the formic byproducts at a certain point
the distillation slows to a virtual stop
and can't continue without raising the
temperature the issue though is that
raising the temperature would favor the
formation of undesired byproducts and as
low as even 115° C the formation of
dimethylamine is favored especially if
excess form Malahide is present to fix
this I go ahead and connect a vacuum to
the distillation apparatus and vacuum
distill away as much as I can until
ammonium chloride begins to crash out of
solution at this point I cut the heat
completely allow my solution to cool the
room temperature and then transfer it to
an ice bath until it's cooled to 0° c i
then passed the solution through vacuum
filtration to collect the ammonium
chloride which can be recrystallized and
reused I then add my solution back to my
boiling flask and continue heating at
105° C and repeat the previous step once
the distillation had again slowed to a
crawl at this point the reaction is
virtually complete and most of the
unreacted ammonium chloride has been
removed to this end I go ahead and move
my boiling flask back to the Heat and
continue heating until the mixture had
reached around 160° C in order to drive
off as much water as as possible this is
then poured into a beaker while still
hot and I went ahead and rinsed the
flask with some methanol to make sure
all my crude methylamine made into the
beaker this immediately began to harden
as methylamine hydrochloride has a
relatively high melting point and to
begin purifying my Creed product I first
needed to dissolve it in a minimal
amount of hot methanol which took around
70 ml in my case now while methylamine
hydrochloride is very soluble in hot
methanol ammonium chloride isn't and
virtually all the remaining ammonium
chloride now be removed by passing this
mixture through vacuum filtration the
resulting solution is left overnight to
crystallize and when I came back the
next day some beautiful methylamine
crystals had formed as a final step I
put this Beaker into an ice bath for a
few hours to crystallize out as much as
possible and then pass the resulting
solution through vacuum filtration to
collect mostly pure methylamine
hydrochloride these crystals are rinsed
with a bit of ice cold methanol followed
by some ice cold D chloromethane to
remove any dimethylamine hydrochloride
that might have formed and then vacuum
desiccated for a few hours vacuum
desiccation is extremely important here
as methylamine hydrochloride is one of
the most aggressively hygroscopic
chemicals I've ever handled and will
pull enough moisture out of the air to
liquefy itself at 40% relative humidity
in just a few hours anyway once my
methylamine hydrochloride was allowed to
dry completely I weighted giving me a
final mass of 16.9 6 G after this I was
able to crystallize out another 10 G
along with 30 G of ammonium chloride
however ever this second batch was
visibly lower Purity with a melting
point of 195° c and not ideal if Purity
is required to calculate percent yield I
decided to use ammonium chloride
consumed as my limiting reagent if I was
left with 30 grams of ammonium chloride
recrystallized the 95 grams were
consumed and my percent yield would be
49.9% out of the theoretical of 53.9 7 G
this yield would actually be considered
quite good based on the literature I've
read but given the quantity of starting
reagents it still feels bad with that
said I don't really love this method it
requires valuable and very toxic
formalin yields are pretty low and it's
very messy smells horrendously of rotten
fish and produces a lot of formate waste
along with a lot of unreacted ammonium
chloride which can obviously be reused
but requires a recrystalization if you
want to use it for anything else as a
side note I did read on one Forum that
this rea can produce yields in excess of
91% if vacuum reflux and distillation is
used exclusively and the reaction
temperature never allowed to exceed 90°
C I found this out after I finished
filming so I didn't try it out and I'm
kind of skeptical of it but I might give
it a shot in the future now the second
method for making methylamine is
basically analogous to the first but
rather than building methylamine from
ammonia and from alahh the methylamine
produced here is formed by the
decomposition of the more comp complex
molecule hexamine to get started on
method number two I added just under 70
G of hexamine fuel tablets to a beaker
along with 170 mL of distilled water
this solution was brought to a boil
under constant stirring until the
tablets had completely dissolved and
then the solution was poured into a
three neck round bottom boiling flask I
then measured out 230 ml of 32%
hydrochloric acid and poured it into an
addition funnel which was connected to
the center neck of the boiling flask the
stop coock was open slightly to allow
the hydrochloric acid to drip onto the
hexamine solution dropwise under
constant stirring until it was all added
this was done because allegedly
dissolving hexamine directly in
hydrochloric acid would result in a much
more aggressive reaction that almost
exclusively forms ammonium chloride
instead the desired reaction here is the
hydrolysis of the hexamine B
hydrochloric acid to form four molecules
of ammonium chloride and six molecules
of formaldahyde the resulting solution
if this reaction proceeds favorably
should be nearly identical to the
solution used in the first synthesis and
so once all the hydrochloric acid had
been added all you have to do is set
this up for a distillation and process
it exactly the same as before this
included another round of slow
distillation at 104° C vacuum
distillation to crash out excess
ammonium chloride filtration to remove
the salt repeat to remove more ammonium
chloride heat to 160° C dissolve in
methanol filter recryst crystallize
filter again to collect the product and
dry however while my footage here
catches up to my lazy explanation I want
to highlight a key difference in this
reaction compared to the first method
now if you'll remember I mentioned that
the formalin solution used in the first
method was stabilized with a significant
quantity of methanol which produced
methyl formate as a primary byproduct
since there is no methanol here and the
solution is far more acidic the primary
byproduct will be formic acid not only
that but the formation of formic acid
here is favorable while in the first
process the oxidation of formic acid to
carbon dioxide was strongly favored as a
result the distillate here contains a
significant amount of surprisingly pure
formic acid which I do collect in the
end and will likely purify later on
anyway once the reaction is complete and
the resulting methylamine hydrochloride
thoroughly processed and dried like
before I went ahead and weighed the
final product for a final mass of 25.97
G of pure methylamine hyd chloride and
another 9.25 G of the impure stuff this
time I was able to recrystallize 21 G of
ammonium chloride and since 10 16.84 G
were generated by the hydrolysis of
hexamine This Means
85.8 G were used in the reaction giving
me a theoretical yield of 48.77 G this
means my percent yield this time was
72.2% although I might knock a few
points off as I don't think I dried my
methylamine is completely in this second
run overall I definitely prefer this
method to the first mostly because the
reagents are way cheaper and easier to
get for me I consistently get higher
yields than I do with the first method
for some reason and the byproduct formic
acid is in of itself much more useful to
me than methyl formate now the third and
final method I have for making
methylamine is by a Hoffman
rearrangement of acetamide this route is
by far the most interesting the fastest
and the cleanest the only caveat here is
that this method is more formally done
using bromine and instead I used
hypochloride as it's worked for me in
the many past hofman rearrangements I've
done on this channel however my yield
ended up excessively low despite the
reaction conditions being controlled
very carefully and that said I believe
that either my acetamide was too impure
or bromine is required for this reaction
to ever be truly efficient if there is
sufficient interest I can retry this
process using bromine and spend a bit
more time verifying the purity of my
acetamide but in the meantime here's how
the hypochlorite route went I began by
dissolving 45.2 G of 73% calcium
hypochloride bleaching powder
representing 33 G of calcium
hypochloride in a minimal volume of
water this is then filtered to leave me
with a reasonably clean solution of
calcium hypochloride and then placed in
the freezer to cool down to well below
0° c i then use a bit of heat to melt
down some acetamide I made a few weeks
ago by reacting acetic acid and Ura in
order to transfer 20 G to a beaker which
is then dissolved in around 40 mL of
water and also placed in the freezer to
cool down as much as possible after a
few hours these are both removed from
the freezer and placed on Ice I transfer
about 105 G of this ice to a large
Beaker and then put that on ice as well
I then go ahead and salt the ice to make
it colder by lowering its melting point
and then I pour my acetamide solution
into the ice spilled Beaker I then wait
until the temperature reads well below
0° C at which point I begin to slowly
add small splashes of my hypochlorite
solution while stirring as much as I can
making sure the temperature is well
below 0° C before adding any more this
reaction is highly exothermic and very
heat sensitive that said if it heats up
even above 10° C you need to scrap
everything and start over in addition
funnel might have actually been an even
better idea here but for some reason I
figured it wasn't worth the extra step
in any case as the hypochloride is added
you'll notice a lot of bubbling which I
didn't really expect my assumption is
that this was D chloramine that was
produced when the hypochlorite reacted
with ammonium acetate impurities in my
acetamide this bubbling ceased after
about a third of my hypochlor had been
added and if this really is the result
of acetamide impurity this accounts for
at least a third of my loss
alternatively there could have been such
a high concentration of hydroxide ions
in my hypochlorite that the reaction
went to completion generating carbon
dioxide but I'm not sure this is
possible this fast and at such low
temperatures anyway the way this should
work is that when acetamide is treated
with an alkaline source of bromine or
chlorine they will react to form in
bromo acetamide or in this case in
chloroacetamide this is a two-step
reaction where first the amine group is
deprotonated by the hydroxide which then
undergos an alpha substitution reaction
with chlorine yielding the
chloroacetamide
once the reaction was complete I went
ahead and poured my reaction mixture
into a three neck round bottom boiling
flask and quickly added my sodium
hydroxide solution which resulted in
even more bubbling in this step the
additional hydroxide abstracts the
remaining amide proton to give the
chloro amide annion the chloro amide
anion rearranges as the methyl group
attached to the carbonal carbon migrates
to the nitrogen at the same time the
chloride ion leaves giving an isocyanate
the isocyanate then reacts with water in
a nucleophilic addition step to yield a
carbamic acid which spontaneously loses
carbon dioxide yielding the Amin product
this reaction is also very exothermic
but not enough to sustain itself
starting from 0° C with that said to
drive the reaction to completion I
gently heat the mixture to around 60° C
at which point it begins to Bubble at
this point the reaction will be able to
generate enough heat to sustain itself
so I remove it from the Heat and allow
it to rest during this time the reaction
mixture Heats itself to the point that
it climbs to nearly 70° cus and if it
were to go beyond this temperature I
would recommend placing the flask in an
ice bath once the reaction mixture
begins to cool the reaction is complete
I then put the boiling flask back on the
heating mantle and heat at 100° C this
will cause methylamine to boil out of
solution which is assisted by excess
hydroxide in the solution the
methylamine gas will then travel through
this apparatus I've constructed and into
cold water where it will readily
dissolve into solution now a couple side
notes while this happens I want to First
clarify that the reason my reaction
mixture turned white after the addition
of the hydroxide was due to the
formation of insoluble calcium hydroxide
and if you were to use sodium
hypochloride or bromine the reaction
mixture would be a pale yellow second
methylamine is aggressively soluble in
its free based form much more so than
even ammonia and that said ref flux is a
genuine concern here which is the main
purpose of the receiving flask I
connected to the end of my short path
apparatus if reflux were to happen it
would simply reflux into the collection
flask and not ruin the entire reaction
third this methylamine gas can also be
fed into hydrochloric acid to yield
methylamine hydrochloride rather than
the free base this reaction however is
extremely aggressive and if you choose
to go this route I would recommend
suspending the funnel above the hydroc
chloric acid rather than in it as I've
done with the water here anyway getting
back to my reaction here you can test if
it's working by testing the pH of the
receiving water with some litmus paper
which should turn blue as methylamine is
very alkaline this reaction is continued
for about 30 minutes until I feel no
more methylamine gases coming over and
then I disconnect my apparatus before
turning off my heat this step reminded
me to reiterate that this should all be
done under a fum Hood as I caught a
whiff of the absolutely foul gaseous
methylamine not only is methylamine one
of the most terrible smelling chemicals
out there it's also quite toxic along
with most of the potential byproducts of
this reaction anyway that's the entire
process and in the end I'm left with a
solution of free base methylamine of
unknown Purity or strength to try and
get an idea of how much methylamine I
actually synthesized I needed to make
this into the hydrochloride salt and
then isolate it to this end I first
neutralized my crude methylamine
solution with hydr chloric acid and
boiled it down until the remaining
liquid was around 145° c i then
dissolved the residue in a minimal
amount of in hydrous methanol and passed
it all through vacuum filtration this
caught a significant amount of what I
can only assume is ammonium chloride
which is discarded the filtrate is then
transferred to a beaker and allowed to
cool so that methylamine hydrochloride
can begin to crystallize out make sure
to pay attention to the shape of the
crystals during this step as methylamine
crystals will form these trans Lucent
feathery crystals while ammonium
chloride will form smaller opaque white
crystals honestly that's something you
should look out for in the previous two
methods as well this is actually the
only footage I bothered trying to get of
methylamine hydrochloride actually
crystallizing and since many of you seem
to enjoy watching these I'm just going
to give this a few more seconds to play
before I resume the
[Music]
procedure
[Music]
anyway once this is killed below
freezing to allow the methylamine to
fully crystallize I collected it by
vacuum filtration and rinsed the
crystals in a minimal amount of
chloroform and ice cold methanol to
remove any impurities I dried the lamine
hydrochloride further under a full
vacuum for a few hours and then Wade
them to get a final mass of just under 3
G or roughly a 133% yield I was able to
more than double this by desperately
crystallizing out the rest of the much
more impure methylamine from the
filtrate but even this new 27.8% yield
isn't very good as I said earlier I'm
nearly positive that my acetamide must
have just been very impure this is
likely negligence on my part as I
figured the Hoffman rearrangement would
be the hard part while the synthesis of
the acetamide itself was basically idiot
proof uh this is clearly not the case
and I might try this again using bromine
and some genuinely pure acetamide in any
case that's all I have for today I hope
you found this video interesting and as
always I want to thank all my incredible
patrons for their generous contributions
your support is vital and very
appreciated this video was done on the
behalf of multiple patreon requests and
do remember that I will eventually get
to every patreon request I've gotten it
just might take a while to everyone else
if you'd like to see more content like
this consider subscribing on Tik Tok
YouTube Instagram or even by becoming a
patron yourself thank you all so much
for watching and I'll see you next
[Music]
time
[Music]
a
تصفح المزيد من مقاطع الفيديو ذات الصلة
What Are Reversible Reactions? | Reactions | Chemistry | FuseSchool
Kuliah Bank dan Lembaga Keuangan - Ep.06 Sewa Guna Usaha (Leasing)
demonstration of exothermic and endothermic reactions
Blockchain Technology
Chapter 2: Chemical Reactions // BIO 221
WATER JET MACHINE PROCESS : Working of abrasive water Jet machining process (animation).
5.0 / 5 (0 votes)