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Sorry for taking so long between posts; my main computer stopped working and it took a while to work out what to replace it with, which then of course meant work to get it working the way I wanted it to. Plus I was feeling a little tired after turning out so many regular blog posts. Fortunately the weather has improved and I can now do some work outside.

Something that has been bugging me for a while now is the mismatch between my own distillation equipment and that shown in period pictures. Some is down simply to it being hard to get anything resembling what is shown, e.g. the metal helms seen in Heironymous Braunschweig’s Book of Distillation. In this case it is because I hadn’t really seen the need to get it, so this experiment and post will serve as something of a test of the new equipment.

So, onto the oil of vitriol. The recipe I am using is one from the THE JESUATTI BOOK OF REMEDIES or LIBRO DE I SECRETTI CON RICETTI , a prior to 1562 collection of recipes made by the friars of the Order of Saint Jerome, compiled by Giovanni Andrew from Brescia, Italy. The recipe can be found here:

I quote it at length because it is so much worth doing so. It is a clear, easy to follow description of how to carry out the process, different from many similar alchemical ones. Perhaps this is because it is for medical purposes.

Take not less than 12 lb. of good, clean Roman vitriol. If you take less you may not recover the expense because it yields not more than one ounce of oil per pound, or about that. Grind it finely because it works better. Then put it in a clean large pot and fill it and push it in as well as you can but do not break the pot. Put on its cover and lute the cover on the pot so nothing can escape and make it so the seal sticks out about the thickness of a finger. Let it dry well in the sun. Then make an oven of bricks walled up with clay in a corner of the fireplace under the flue of the chimney and do it in the way that you see here. Fit your pot in the middle and close up around it with bricks that are vented only by one little hole behind. Make a fire of dry wood underneath and burn it very slowly for one whole day, that is 24 hours and let it cool. Then open the oven and draw out your pot. Be careful, before you break the pot in order to remove the vitriol, to have first prepared a large bronze mortar and a sieve covered as it is for spices and a large curved retort as you see. As before, it must be well sealed with lute of wisdom and the neck of the retort hangs out of the oven through an opening.

First break the pot which otherwise you would not be able to empty because all has been made into a hard mass of red that looks like powdered brick. Be quick to grind it and sieve it and put it in the retort. This is done so that it takes up little air because it is affected greatly by air so that it does not render the oil sufficiently and if the powder was coarsely sifted it renders less oil. You are warned about all these things. When you have put all this powder in the retort, place it in the oven as you see, so it lies along the length of the oven. The bricks that are used underneath are unbaked and are one finger apart, one from the other, and all the way around it is walled well with bricks and clay and it has a narrow little opening behind and a small opening in the front. At once put the largest receptacle you can find in respect to the great outburst of vapours that comes suddenly at the end. If it is small it would be broken from this sudden outburst but it works the way I tell you. Make the fire in the middle of the oven and be advised that the fire controls everything. Make the fire very slow and with dry wood. If it is not dry, do not use it and, if possible, it should not be one stick each time but at least 2 if you can put them there. Always stir it up one at a time, continually if you see them touching. Never leave the fire and never let it stop burning and keep it always steady. Be warned about this because it is very important. Never leave the fire to burn by itself and at night one must always watch because it must not lack care for 6 days to make it perfect and good. With all this care it will never show you a sign except on the fifth day the spirits will begin to come forth and to come out into the receptacle with great force……

because having closed the opening of the receptacle securely with luted cloth all around, the gases cannot escape. Also it is better if the receptacle is large. Here is an ingenious secret so that the receptacle may not be broken by the great heat when the gases are entering. Devise a way that cold water is always dropping on the receptacle and in this way it or any other receptacle will never crack. Be advised that if you do this dropping of water, in 4 or 5 days you will have oil more quickly. If you do not do this dropping of water, you must wait to the fifth and sixth day and then all the gases will come at once. It is a frightening thing to see such dark smoke fill up all the receptacle which then condenses below and soon is reduced to oil. This oil is blackish in colour or dark tan and take this, with the aid of God and with speed and dexterity, and extract it from the receptacle and put it in a large glass bottle and secure it because this oil is a very fiery and active spirit. Keep it covered with great care with new or white wax and with 2 or 3 layers of parchment doubled and well tied, because in truth all the spirit may be lost quickly in fumes and be gone.

The first question is, Roman vitriol, do they mean copper or iron based? Probably iron based, perhaps with some copper mixed in.
So, in order to mimic the first stage of heating in an oven, I put a blowtorch on the vitriol whilst stirring it, so it turned a bit red:
green vitriol after blowtorch april 2015

This will have boiled off some of the water of crystallisation, that which is trapped in the crystals as they form, attached to the iron sulphate.
Of course the actual practise is a bit different. Actually truly sealing it in a vessel and heating to several hundred degrees might produce an interesting product, and I don’t know what it would be except that it would contain iron and sulphur. The fact that a red substance is referred to makes me think that it is unlikely that the jar was really sealed, and a lot of vapours will have left it when it was heated leaving behind iron. Of course I also suspect that a truly sealed jar heated with vitriol inside would explode due to the pressure; this sort of accidentally getting a specific outcome without really meaning to happens a lot in the early history of technology.

Next, I heated it in this setup:
Sulphuric acid setup alembic full april2015

Note the large vessel on the right to catch the vapours, it is the new acquisition I made from ebay. It is a cylinder, possibly of pyrex, of about 12 litre volume, with only one entrance at the top. I have no idea what it was made for, neither had the seller. I suspect it is from some medium sized chemical plant operation. It mimics the large receiving vessels you see in 16th century works that give a good volume for the collection and condensing of vapours. I didn’t feel any need to run water on it though, the vapours condensed by themselves as everything cooled down. You can see that I took this photograph during the process, with the alembic filled with white fume.

I started the fire, and in ten or so minutes was reaching over 400C, and I turned it up until it was over 600C. By that stage some vapour was condensing, but it looked rather like water. This would be the remainder of the water of crystallisation.

So I kept on heating, and after another 5 or more minutes, some of that with pulses of heat at 700C and more passing through the cucurbit (The lute slows down heat transfer, so it can take a while for whatever is inside to reach the proper temperature), a nice white vapour came off and filled the alembic, as seen earlier.
Then it trickled into the vessel to condense. Unfortunately there wasn’t much of it, but I got some nice videos of the likely sulphuric acid fumes rolling out of the tube into the vessel:

I love the way it puffs out of the tube. The end result was a cloud of sulphuric acid vapour:

sulphuric acid vapour april2015
The pH of this liquid was 1, i.e. nice and pure. But it is a clear liquid:
sulphuric acid april2015

I have a theory that the redness mentioned in the text is due to iron being blown over from the furnace into the collector. The inside of the cucurbit is like this:

sulpphuric acid april2015 inside cucurbit
I think some of that redness is due to the iron oxide being blown up the neck of it. Putting some of this iron oxide into the sulphuric acid turned it red:
sulphuric acid with iron april 2015

Which isn’t surprising. However I have to add a note of caution here – there is also the possibility that some sulphur compounds, polymers left behind by the earlier calcination of the sulphate would help colour the acid. On the other hand I suspect it would leave a more obvious sulphurous encrustation on the vessels involved, so seems less likely to me. What really convinces me it is sulphuric acid though is that the virtues of it are:

If you put a drop on a cape or clothing that was in 4 or 6 or even in 10 folds, it consumes all in this way. At first you do not see any sign but if you examine the garment, all the holes are seen where the fabric was consumed completely.
As I know from spilling battery acid on myself as a child, it eats away your clothes.
I don’t actually feel like testing this:
If you put 2 drops in a glass of sweet wine, it will remove the sweetness at once and give it a certain burnt flavor very appetizing to taste. It gives you a very good stomach and will make you look younger and with very good breath. It clears the eyesight and preserves the memory. It removes corns rapidly. This has been tested.

But the use of it on corns makes sense because sulphuric acid eats organic material very well.
Note the emphasis on it having been tested. By the 16th century this was something that everyone was interested in, things that worked and had been tested. Not that they didn’t think about that before, but I get the impression, as part of the spread of knowledge, that something having been personally tested by a trustworthy person was an important thing.

The thing is that it is something of a mixture of old and new. Sulphuric acid wasn’t really known about in the west until the 14th century or so, and I doubt it was used medically until after the writings of John of Rupescissa became popular, i.e. into the 15th century, with the mixing of herbs with amazing new powerful waters or rather quintessences. Another virtue of it is:
It is useful to cure all kinds of fever when given before the paroxysm with a decoction of centaury and of rosemary cooked in wine. It cures the quartan fever when it is boiled with myrrh.

Which is a mixture of old and new medicine, the use of herbs and the amazing new liquid. The funny thing though is that I had a look through “The book of the quintessence” and “Healing and Society in Medieval ENgland” and “A leechbook or collection of medical recipes of the fifteenth century” and the cures they have for fever use different herbs than this recipes does. Perhaps that is due to local variations in access to and belief in specific herbal remedies.
If you are thinking that this all seems quite a complex operation requiring a large furnace and good glassware, just for medical purposes you would be correct. But I searched for “distill” in the online version and found 162 instances in the recipe section. Many are mere distillations of herbs, others of wine with stuff in it, and others again are “Take a pound of clear and good honey, an ounce of ground pepper and a quantity of fresh roots of reed and distill them. “ which is a “Remedy to make hair grow after a disease causing baldness, tested in Lucca, 1559” (http://etext.ku.edu/view?docId=jesuatti/jesuatti.xml;chunk.id=id212413;toc.depth=1;toc.id=id114325;brand=jesuatti;route=jesuatti;query=distill#1)

So it is more evidence of the importance of distillation in medicine. It had developed a lot since the 13th century, but also owed a great deal to the alchemists for their practical skills and knowledge.
I shall be continuing with alchemical recipes over the next few months, so watch this space.