Basic Chemistry

[acolon_5]

There have been quite a few questions about basic chemistry.

For instance what is a salt, acid, or base are. Same goes for terms like pH, pKa, weak acids, weak bases, conjugate acid/bases, titration, polar and non polar solvent, oxidation, reduction etc. etc.

We have some very knowledgeable folks here that are willing to help answer your, your friends, your friends pets, and my questions on the subject.

Please keep this thread on basic chemistry. Synthesis discussions are not allowed!! Any posts relating to or hinting at synthesis, precursors or the like will be edited and the poster will be given a warning.

 

[Infundibulum]

OK, as I promised, I start first:

The topic is about what is pH, then I will move to what acids, bases and salts are.

First of all, it should be noted that almost everything in the "extraction" chemistry can be considered as a "reaction". For instance, one can start with the materials A and B which react to give us C and D.

We usually write this as

A + B -> C + D

This is called an irreversible reaction (note the "->" arrow)

Plenty of reactions can also be reversible and the correct way of writing them is:

A + B <-> C + D

Please try to keep this in mind. Also try to keep in mind that the above equation can be simpler ( e.g. A -> C + D)

When we consider extractions, it is useful to think that all the molecules are a composite of a "positive" and a "negative" ion. Everyone can more or less understand that positive attracts negative. Table salt is written NaCl and it is actually the composite of a positive ion (Na+) and a negative ion (Cl-)

And even water can be seen as a composite of a positive and a negative ion!

The water molecule is H2O, (that is 2 hydrogens, H and one oxygen, O) and can also be written as HOH. And water molecule can spontaneously break down to a positive and negative ion;

HOH -> H+ + OH-

But in reality this is a reversible reaction, so we write it:

HOH <-> H+ + OH- (more correctly, this is written as HOH + HOH <-> H3O+ + OH-)

So one can actually think water as a composite of HOH, H+, and OH-. And this is actually where pH is coming from. pH is the concentration of H+ in a solution, pOH is the concentration of OH- in a solution.

Now, pH is a nasty term for people who hate mathematics. The easiest way to put it is that it is a scale in which the lower it is the more H+ you have in a solution, the higher it is the less H+ you have in a solution. The pH scale in itself is weird! It is called a logarithmic scale, now forget you read this term! What it means is that:

you have 10x less H+ as you go one number up. In practical terms, if you have a solution with pH=1 this has:
10x more H+ than pH 2 or
100x more H+ than pH 3 or
10x less H+ than pH 0

Now, water has a pH of 7 as we already know. This is the midpoint and can only be changed if one adds more H+ or more OH- to the solution.

NOTE: It is straightforward to see that one can add H+ in the water and lower the pH (or so to speak increase the amount of H+). It is less straightforward to understand how you can increase the pH (or reduce the amount of H+) by adding OH-. And personally I do not have a way to explain it in very simple terms. It has to do with water's dissociation equilibrium and how a reversible reaction can be "driven" towards one or the other direction, blah blah blah, just forget it if you think that all the above information is too much!

 

[Infundibulum]

Now it is going to be about acids, bases and salts.

Acids and bases are molecules that can be seen as a combination of a positive and a negative part.

Examples of acids are:

Hydrochloric acid: HCl which contains H+ and Cl-
Sulphuric acid : H2SO4 which contains 2H+ and SO4--
Phosphoric acid : H3PO4 which contains 3H+ and PO4---

Examples of bases are:

Sodium Hydroxide : NaOH which contains Na+ and OH-
Potassium Hydroxide: KOH which contains K+ and OH-
Calcium hydroxide : Ca(OH)2 which contains Ca++ and 2OH-
Ammonia : NH3 which contains ....well read below!

(note that one "-" or "+" means "one unit of the respective charge", and "--", "++" means two units of the respective charge. This is because these molecules in their purest form are neutral, e.g. the double positive charge of Ca in Ca(OH)2 is balanced by two single negative charges from the OH)

Both acids or bases can be divided in strong and weak acids or bases. The distinction manifests if one observes the behaviour of the acid or base in the water:


Strong acids and bases break down (or more correctly "dissociate" fully in water. This is an "irreversible reaction"

Weak acids and bases do not dissociate fully in water. This is an "reversible reaction"

Examples of strong acids are HCl and H2SO4. Their behaviour in water is:

HCl -> H+ + Cl- and
H2SO4 -> 2H+ + SO4--

Examples of weak acids are acetic acid, phosphoric acid and citric acid:

Acetic acid : CH3COOH <-> H+ + CH3COO-
phosphoric acid: H3PO4 <-> 3H+ + PO4--- (this is NOT the correct way to write it! it is written as such for illustration)
Citric acid : (can't be arsed to write down)

Examples of strong bases are NaOH and KOH:

NaOH -> Na+ + OH-
KOH -> K+ + OH-

and examples of weak bases are ammonia and DMT(!)

NH3 + HOH <-> NH4+ + OH- (weird, eh?)
DMT-N + HOH <-> DMT-NH+ + OH-

Now one can see that a strong acid (like HCl) can bring pH down to 3, 2, 1, 0, and even -1. This is because the all the acid will dissociate, so the more you put the more H+ you will eventually provide into the solution.

Weak acids behave a bit differently... So, one dissolves some acetic acid in solution and this will initially dissociate as in CH3COOH -> H+ + CH3COO-. The more you add, the more will dissociate, UP TO A CERTAIN POINT, where the acetic acid will say "hey, im supposed to be weak stuff, I cannot dissociate forever! And this is the point at which the reverse reaction starts, or H+ + CH3COO- -> CH3COOH to establish the final equilibrium: CH3COOH <-> H+ + CH3COO-. After this point, adding more acetic acid will NOT change the pH because it will stay "associated" (CH3COOH) and will not be able to provide more H+ to the solution. (In the end I couldn't avoid talking about reaction equilibria...anyways!)

Strong and weak bases are the exact same thing (in reverse of course!) So one can go up to pH 13, 14, maybe ~15 using NaOH which will always dissociate to Na+ and OH-, while other bases like NH3 can only go up to a certain point)

NOTE: Sodium carbonate is not a base; it is a salt, but it behaves like a base! It is called a conjugate base and we can talk about it in the salts saction)

 

[Infundibulum]

And salts are the children of acids and bases...

Generally speaking an acid will react with a base to produce a salt and water. If a HCl reacts with NaOH the product will be:

HCl + NaOH -> NaCl + HOH

(Note, positive elements are in bold, negative elements are underlined

And it is not a surprise that table salt, NaCl can be seen as a compound containing a positive and a negative entity...

And there are thousands of other salts, like DMT-Cl. You remember that freebase DMT is a base, actually a very weak base. Historically, alkaloids were called as such because the have weak alkaline (= basic) properties. DMT-Cl can be formed by the reaction between hydrocloric and dmt.

Some of the salts can have weak acidic or basic properties. Those salts are the children of

1) weak acids with strong bases and they are called conjugate bases and
2) strong acids with weal bases and they are called conjugate acids

If one marries carbonic acid ( a weak acid) to NaOH (a strong base) will get sodium carbonate:

H2CO3 + 2NaOH -> Na2CO3 + HOH

And how does sodium carbonate provides OH- to the solution thus making it more basic? Well, many of the salts are soluble in water (not all though!) and sodium carbonate "dissociates" in water (= dissolves) as such:

Na2CO3 -> 2Na+ + CO3--

Then, this CO3-- that came from its parent the mr weak carbonic acid has the tendency to react with water in an attempt to revive mr weak carbonic acid. By doing so, it creates OH-!!
This is written like:

CO3-- + 2HOH <-> H2CO3 + 2OH-

and those OH- make the pH basic but not infinitely, since as you may observe the latter reaction is reversible.

NOTE: in reality things are a bit more complicated; the above example of how one can basify with sodium carbonate is oversimplified to provide a very simplistic explanation. Do not write it like that in a chemistry exam!!!

Other salts that can basify a solution are sodium phosphate, sodium citrate, sodium acetate etc.

In reverse, ammonium cloride (NH4Cl) is a conjugate acid (child of a strong acid, HCl and a weak base, ammonia NH3) and can be used to weakly acidify water.

 

[Reborn]

Holy crap, Chem 101 all over again,... NO NO.
Just kidding sorry couldn't help it.
Great start guys.

Just a reminder, if you start testing the pH of things just for fun and realize that your water is either basic or acidic (usually acidic) don't freak out, even if its 100% pure distilled. Water has no buffering capability so even small quantities of gases (such as CO2) that dissolve in water can change the pH easily.

So what is a buffer.
Buffer-Buffer solutions are solutions that resist change in hydronium ion and the hydroxide ion concentration (and consequently pH) upon addition of small amounts of acid or base, or upon dilution. Buffer solutions consist of a weak acid and its conjugate base (more common) or a weak base and its conjugate acid (less common). The resistive action is the result of the equilibrium between the weak acid (HA) and its conjugate base (A−):

HA(aq) + H2O(l) ↔ H3O+(aq) + A−(aq)

The human blood is a buffered solution, if your pH of your blood goes off you get very very sick. All fluid in living things are buffered, because pH must be maintained for survival.

 

[Infundibulum]

...hahaha, now I will talk about reaction equilibria which is very important in understanding the behaviour of dmt in solution. And I will use dmt as an example as well.

Dmt is a base. Tiny amounts of it dissolves in water and can make pH more basic. the reaction is

DMT-N: + HOH <-> DMT-N:H+ + OH-

This is a reversible reaction due to the fact that DMT is a weak base. And it has an equilibrium, which is sort of like a "balancing point". In the simplest terms it means:

There is as much DMT dissociating to DMT-N:H+ + OH- as there are DMT-N:H+ + OH- associating to form back DMT.

So, the freebase form is in equilibrium with the dissolved form. This ALWAYS happens in any acid or basic solution you may think!

But what actually controls this equilibrium? Why would one care? One would care if he wanted to "push" the equilibrium to the left side of the reaction so that he gets more of the freebase than than the dissolved form.

Now it may get a bit difficult...Reaction equilibria as we said have this inherent balancing point and this is dependent on how much you have from each DMT-N:, DMT-N:H+, and OH-. Which means that if you get an already established equilibrium you have the ability to modify it as long as you "twitch" the amounts of DMT-N:, DMT-N:H+, and OH-. An example is needed here:

NOTE: do not think of pH and solubility of the freebase at this moment; Just think that one has a water solution (pH 7) which has some dmt dissolved into it. The dmt will dissolve and quickly go to the equiligrium

By considering therefore this solution, it looks like that:

DMT-N: + HOH <-> DMT-N:H+ + OH-

If one puts more freebase in this solution, then the reaction will get unbalanced; the left part will have more DMT for a moment; The reaction will be then "shift" to the right which means that part of this newly added DMT freebase will dissolve to DMT-N:H+ + OH- in an attempt to restore the previous equilibrium.

But one can play with this equilibrium in other ways as well! One can put more DMT-N:H+ ; The reaction will get unbalanced again and DMT-N:H+ will try to associate with OH- to form freebase DMT. Same goes for OH-; if one puts more OH- in the solution reaction will get unbalanced again and OH- will to try to find some DMT-N:H+ to make DMT freebase.

Everyone can now see that the latter is what everyone is dreaming about doing. Add more OH- in the solution (= basification) and push the equilibrium of the reaction to the left, hence creating more freebase alkaloid.

But people actually dream of playing with the equilibrium in more diverse ways. As one can see considering the dissociation reaction of DMT in the solution, if one "takes away" DMT freebase from the solution, then the reaction will become unbalanced; DMT-N:H+ and OH- will associate to replenish this "stolen" freebase.

And again, people already know about dreaming of how to steal dmt freebase from the solution; they take advantage of the fact that the freebase is very insoluble in water but fairly soluble in non-polar solvents to steal the freebase from a solution. What effectively happens then is that any water-dissolved DMT-N:H+ and OH- will associate to form more freebase and restore the equilibrium.

And the latter is exactly what 69ron has mentioned and also tried to explain quite a few times. One does NOT need extreme pH values e.g. above 11). As long as one makes a few good pulls with non-polar solvent, one should be able to get almost everything out at pH 9.

I have not yet talked about pKa. pKa is just a calculated value to show you the pH at which a weak acid is half in the associated state (e.g. CH3COOH for acetic acid) and half in the dissociated state (i.e. CH3COO-). Bases have a pKb and DMT as a base has a pKb (but it doesn't hurt anybody to call it pKa so I'm gonna call it as such;D) which is 8.68. Which means that at a pH of 8.68 half the DMT will be freebased (DMT-N and half dissociated (DMT-N:H+).

In theory therefore, one can pull DMT using the non-polar solvent at pH of 8.68. By doing so, the equilibrium will be affected, then more of the dissociated form will turn into more freebase ready to be scavenged by the second NP pull..!

 

[endlessness]

what happens if a substance that is already in salt form (such as dmt in mimosa, hypothesized to be dmt tannate, according to 69ron), is put in a medium with another kind of acid (such as vinegar, or hcl).. Does the dmt change to acetate or hcl, for example, or does it continue being the original salt?

 

[acolon_5]

^ I've wondered this myself. Will a weaker acid make a new salt (DMT HCL + Acetic Acid -> DMT Acetate + ?) Will a stronger (DMT Acetate + HCL -> DMT HCL + ?)

 

[moracca]

Ok so i have a question for you guys...

When DMT is in salt form, for example HCl form... What exactly does that mean? i mean, I understand the concept of the free base and the different salt forms, but like, what exactly is a salt of a particular compound? Does the molecular formula change somehow? do the molecules align differently? Is it a mix of DMT and HCl? Do the planets align differently?? Thats one thing I never really understood. thanks in advance!

 

[Infundibulum]

what happens if a substance that is already in salt form (such as dmt in mimosa, hypothesized to be dmt tannate, according to 69ron), is put in a medium with another kind of acid (such as vinegar, or hcl).. Does the dmt change to acetate or hcl, for example, or does it continue being the original salt?

Yes, in theory ACID + SALT -> NEW ACID + NEW SALT, so dmt acetate mixed with a HCl solution is going to produce dmt chloride and acetic acid.

This is the case when (as acolon said) dmt salt goes from "product of a weaker acid" to "product of the stronger acid"

 

[burnt]

When DMT is in salt form, for example HCl form... What exactly does that mean? i mean, I understand the concept of the free base and the different salt forms, but like, what exactly is a salt of a particular compound? Does the molecular formula change somehow? do the molecules align differently? Is it a mix of DMT and HCl? Do the planets align differently?? Thats one thing I never really understood. thanks in advance!

All it means is that the compound in this case DMT is ionically bound to the charged Cl atom. In solution HCl dissociates so you have H+ and Cl-. Also in acidic solutions the Nitrogen on DMT becomes positively charged so it can form a ionic bond with Cl-.

 

[soulman]

Can someone please explain simply, if you can go STB, what is the purpose of the acid in the A/B extractions?

 

[burnt]

^^Sure.

You can do STB and skip the whole acid part. The acid part does offer one advantage. That you can defat your acidic extract with a non polar solvent. Defatting helps remove fats and lipids which could make doing a STB annoying if you get a bad emulsion as a result of fats/lipids.

 

[Jorkest]

unless you finish off with FASA

 

[Infundibulum]

^^Sure.

You can do STB and skip the whole acid part. The acid part does offer one advantage. That you can defat your acidic extract with a non polar solvent. Defatting helps remove fats and lipids which could make doing a STB annoying if you get a bad emulsion as a result of fats/lipids.

SWIM's FOAF thinks there are few more reasons as well:

1) The very first part in extraction is to get whatever you extract out of the plant material and into a solution. Plants have cell walls that need to be broken down somehow and the component of plant cell walls is one of the toughest in nature. Different plant cells (e.g. root bark cells vs leaf cells vs seed cells) also have different cell walls.

Boiling (especially in acid conditions) will brake all of them down. They will easily burst due to osmosis. This, as far as the acid part of an A/B is concerned. In STB, a fairly high pH is required to brake open the cell walls and release the goodies.

But the latter is relative as well. Root bark certainly needs high pH (i.e. >13) for this to happen. STB using weaker base will not really work that well if it ever works. Seed material seems to contain cells walls that are easier to destroy with a lower pH. That is why a sodium carbonate/calcium hydroxide-seeds watery paste works. It is an STB technically speaking. As far as leaf material is concerned, it can be effectively extracted with STB using a strong base, but SWIM's FOAF is unaware whether weaker bases could do as well.

2) Since STB's tend to employ high pH values, certain alkaloids that are unstable at those high values may get destroyed. Consensus theory would say that one would not extract psilocin from mushrooms using STB because it can potentially destroy the alkaloids.

But yeah, when working with MHRB STB is equally reliable and much faster than A/B, as long as one has access to NaOH.

 

[soulman]

But yeah, when working with MHRB STB is equally reliable and much faster than A/B, as long as one has access to NaOH.

Sweet, ill just stick o STB then. Thanks for the info guys

 

[acolon_5]

I have 2 basic chemistry questions.

1) How does one make a 5% solution (for example) with water and a solid. What is the correct ratio?

5grams to 100mL?

2) how does one make a 5% solution with a liquid and a liquid....say concentrated sulfuric acid and water?

5mL S2HO4 and 100mL water?

This is real basic stuff, but I really don't have much knowledge in chemistry.

Thanks!

 

[Infundibulum]

Almost correct!

A 5% solution of a solid dissolved in a liquid is more correctly written "5% w/v".This basically stands for 5% weight per volume.

So, to make a 5% salt solution one needs to dissolve 5 grams of salt per 100ml of water as you said.

Things get slightly more complicated in the second case, which is, say making a 5% solution of a liquid dissolved in liquid.Again this is more correctly written "5% v/v" or 5% volume per volume.

In this case one needs to consider that addition of a liquid in another liquid will increase the total volume of the liquid.For instance, say one needs to make a 5% acetic acid solution in water. Both pure acetic acid and water are liquids.

The wrong way to do it is to add 5ml acetic acid in 100ml of water.In this case, the total volume of the final solution will get to 105 (that is, 100ml water + 5ml acetic acid). In this case, 5ml acetic acid are contained in 105ml of total volume and the solution is actually 5 / 105 = 0.047, or 4.7% acetic acid.

The right way to do it is to add 5ml acetic acid in 95ml water. Now the final volume is 100ml, out of which 5ml are acetic acid. This is exactly 5%.

It is the volume increase that complicates the latter case of v/v a wee bit. In the former case of w/v, addition of, say, salt in the water is not assumed to change the volume of water. This is not quite correct, but it is assumed to be correct for practical reasons.

As a matter of fact dissolving a solid in a liquid slightly increases the volume of the liquid. If one requires extreme precision and wants to make an EXACT 5% w/v of, say, salt solution the strategy is as follows:

1) dissolve 5g of salt in 80 to 90ml water.
2) Carefully bring the volume to exactly 100ml by adding more water.

But again this method is only suitable when extreme precision is required or if one is obsessive-compulsive.....

 

[acolon_5]

Thanks Infundibulum!

That clears some things up for me.

 

[Entropymancer]

Almost correct!

A 5% solution of a solid dissolved in a liquid is more correctly written "5% w/v".This basically stands for 5% weight per volume.

So, to make a 5% salt solution one needs to dissolve 5 grams of salt per 100ml of water as you said.

That's not precisely correct, you're neglecting the change in volume that results from dissolving the solid. To get a true 5% w/v solution of saltwater, you'd dissolve 5 grams in ~90 mL water, then once it's dissolved, add water until you reach a final volume of 100 mL.