The details of his life are obscure and derive mainly from his detractors.
He was born in Herford (Westphalia) at an unknown date, and went in 1640 to Holstein and Prussia where he served as apprentice in apothecaries. In 1644, he went to Italy, where he received an M.D. from Padua University in 1652, but later he settled in Venice. It seems that his main means of support was the selling of a "viperine salt" (Sal viperinum) as a sovereign remedy.
Being several times attacked on the novelty and efficacy of his preparation, he replied in a book, "Hippocrates chemicus", a defense of the "viperine salt" including a long discussion of the nature and use of alkalis.


Tachenius book : Hippocrates chymicus

appropriated for everybody
are clearly and profusely explained
the most ancient basis of the new snake salt
as well as the nature of acids and bases.
To that new edition
was added a double index
one for the chapters, the other for 
the memorable things
which should be useful for the reader.
Lutèce, city of Parisians
At Joannes d'Houry house,
At the end of the Pont Neuf, 
close to the RR.PP. Augustins monastery

He was interested in salts which he considered not as alchemists as an essential constituent of matter, but as a combination of acid and alkali. As he recalled in his famous book, the name alkali comes from the Arab name Kali, a small plant growing in Egypt (Salsola kali, chaenopodiaceae) which gives after burning a salt, "al kali" (then alkali).
Later, Tachenius elaborated his theory of alkalis which stated that acid and alkali are the two principles of all things. According to him, they correspond to the fire and water that Hippocrates found in all things. His main work is of importance for the description of methods of soap, ammoniac salts, and corrosive sublimate production.
While soap was known in the ancient Egypt, surely 15 centuries B.C. (Ebers Papyrus), its chemical composition remained obscure until the 19th century. For lipidologists, the main contribution of Tachenius to soap knowledge, and hence to organic chemistry, was to have suggested that saponifiable fats could contain a hidden acid ("acidum occultum"), about 150 years before the discovery of the true nature of soap and triglycerides by Chevreul.

We give below the Latin text of the chapter of Tachenius book where he reported how to make soap in mixing oils or fats with a concentrated alkali solution previously obtained from plant ashes.
The date of his death is unknown, probably around 1670.

Alcali et oleum fit sapo


Calx, ut dixi, habet duas diuersas facultates acidum et alcali : alcali habere saltem saponariam et abstersiuam virtutem supra dixi, quam extrahere et separare docuerunt Hippocratici suo famili. Saponarii itaque addunt calci, Alcali factitium, ex vegetabilibus exutum, in tripla proportione, eo quod acidam partem in calce morrificat, et alteram suo simili liquat. Humectant itaque cineres alcalizatas pauxillum, quibuscum cooperiunt calcem inextinctam ; sic relinquunt, donec calxdehiseat, pro signo mutuae actionis, tunc commiscent, assunduntque aquam, ut massa humidior fiat, juxta regulam ; salia non agunt nisi dissoluta : tunc sufficienti aquae quantitate, extrahunt alcali lixiuiale igneum (igneum dico, cosumpsit enim in momento bulliens hoc lixiuium ebrium hominem, cum laneis vestibus, ut nil repertum fuerit, praeter lineum undusium, et duriora ossa, ut accepi a fide digno, huius artis professore) quod lixiuiuim igneum, Magistram vocant ; quae tanto alcali saturata, ut ovum in illa non submergatur. Ex eadem mixtura sit et aliud lixiuium minus saturatum, quod ovum non sustinet ; cum ultimo hoc, oleum vel pinguedinem (alcali contrarium, acidum enim occultum continet, ut apperebit paulatum) primo commiscent (propter suas causas) coquendo saponem ; coquunt, inquam, lento igne donec albescunt tunc adijciunt pinguedinis proportione : coagulat autem bulliendo oleum alcali, donec in unum corpus coeant, ut contraria et permixta ; nunquam enim simul in eodem consistunt, sed semper alterantur : necessarium est etiam, quae ab ipsis secernuntur, ac producuntur dissimilia fieri, ex alcali nimirum manifesto, et acido occulto in oleo sit aliquid neutri, salsi saporis : lingua quandoque explorant, si sapor dulcis, addunt Magistram, si mordax coqui debet, donec oleum absorpserit, sin vero mordacior, sensim addunt oleum ad discretionem, ut docet Hippocr. spiritus alter, inquit, trahit, alter protrudit, idem autem uterque facit, in utramque partem tendunt, sic hominis naturam imitantur. Sal maris, quia non est corpus vacuum, ut alcalia, cum pinguedine in saponem non coagulatur ; habet enim ambas facultates difficulter separabiles, ut postea ostendam ea de causa Nausicca, Alcinoi filia lauabat lintea ex fonte in maris littore, ut habet Homerus odyss.

Alkali and oil give soap

Chapter III

As I said before, lime has two different properties : those of an acid and of a base. I said above that alkali has the property of soaping and cleaning, properties that Hippocrates followers have learnt to separate. Thus, they add to a soapy lime three volumes of an alkali prepared from plants, because it neutralizes the acid contained in the lime in entering in combination. They wet slightly the alkaline ashes, add more product until the lime becomes slaked, they wait until the crust cracked and then pour again some water according to the rule "the salts are reacting only in solution". Then, with enough water, they extract that burning lye (I say burning because it happened to a tipsy man wearing a wool dress to be burnt so quickly by that hot lye that only a linen shirt and his bones were recovered). That burning lye was named "Magistra". Alkali is so concentrated that an egg remains floating. A more diluted solution is prepared which does not enable an egg to float. To that solution, oil or better fat is added (fat contains a substance opposed to alkali, i.e. a hidden acid as it be clear later on) while boiling that soap mixture. A gentle boiling is maintained until bleaching of the solution, then three volumes of oil or fat are added. The alkali and oil clot together during boiling until they form only one substance composed of opposite compounds. From the alkali, which is visible, and the acid which is hidden in oil, some compound is produced which is neither the former nor the later but has the taste of a salt. When one tastes with the tongue, if the flavor is sweet, the "Magistra" solution is added, if biting, oil is added until completely absorbed, if very biting, oil is added gradually until a separation is observed. As Hippocrates said, a spirit pulls, another pushes but each one does the same thing, they extend toward the reverse direction and, thus, they mimic the human disposition. Sea salt, since it is not an empty substance as alkali, does not combine with fats to form soap. Its two properties are non easily separated. That is the reason why Nausicaa, the Alcion daughter, could wash her clothes in a sea shore spring, as it is written in Homer Odyssey.