What is the Italian ‘Acido Psammico’ (Psammic acid?)

I am reading an Italian detective novel — [*Lo stato delle anime* by Giorgio Todde](http://www.ciao.it/Lo_stato_delle_anime_Giorgio_Todde__Opinione_1104970) — in which someone is poisoned with ‘acido psammico’.



> 
> Marini trova nello stomaco della vittima un ostia con all’interno dell’**acido psammico** (usato per conciare le pelli), l’acido ha ucciso la donna avvelenandola.
> 
> 
> 


Which I think translates into English as:



> 
> In the stomach of the victim Marini finds a communion wafer, inside of
>  which is ‘psammic acid’ (used to tan hides): the acid had killed the
>  woman by poisoning.
> 
> 
> 


I have spent quite a time with dictionary and Google searches using the Italian, French (acide psammique) and English (psammitic acid comes up but is not defined) terms without success. The term ‘psammico’ seems to come up in a geological context, but infrequently and without clarifying things.


I should add that the novel is set in rural Sardinia in the 1890s and the implication is that shepherds would have access to it.


Does anyone know what the modern name and chemical composition of this is?


**Addendum: Further Information**


I am now reading further in the book (slowly, very slowly) and on p. 101 the protagonist (Marini) is in the capital city (Cagliari) and enters a chemist’s (pharmacist’s) shop to ask for ‘acido psammico’. He receives the following reply:



> 
> La sabbiolina mortale?
> 
> 
> 


In which ‘sabbiolina’ (not in my dictionaries) appears to be a diminutive related to ‘sabbia’ — sand. (‘mortale’ = ‘deadly, fatal’, of course.)


Consistent with this, further down the page we have:



> 
> La sabbia velenosa…
> 
> 
> 


“The poisonous sand…”




(Edit: this answer turned indeed to be the right one)


Italian *Psammico* - from the greek *Psámmos* for Sand - reads as "sandy". It can thus refer to a soil or the organisms living in or about sandy soils and waters, or to something derived from sands. 


We as chemists know that sand is mostly silicates, so it seems difficult to think of a poison.


However if we take "sand" as to mean "from the soil, mineral, inorganic" and combine this with the fact that the most historical and literary mineral poison is Arsenic, than I would suggest that the character has been killed by As2O3 or some other compound containing this element.


Arsenic and its compounds can (were) indeed use to tan skins and leathers, to preserve wood and timbers, and even in mummification processes.


In particular Wikipedia mentions cupper arsenochromate as a (modernly banned) ingredient in non-tannin based tanning. 


At least in XIX century Italy, the word "acid" could have referred to non formally and/or non chemically acid compounds. Given the negative connotation of the word among those workers with no chemistry background, acid could have referred to any dangerous substance. Alternatively, it could have referred as it does today, to accepted traditional nomenclature or dehydrated forms, like in the case of tannic acid or in that of As2O3, respectively.


My answer remains speculative but I think has quite reasonable bases. The novel author in this case did not use any license, just found a more cryptic and archaic but "original" name for arsenic as poison.


 10

Actually, the meaning is: 



```
used to tan leather.

```

The acid used traditionally in tanneries is tannic acid, from there its name.


Tannic acid can be found in several plants one of which is the Sicilian Sumac (*Rhus coriaria*). This plant is also found in Sardegna (as per [Flora Italiana](http://luirig.altervista.org)), where the novel is placed.
The Italian name for this shrub is Sommacco siciliano.
The description of this plant is:



```
piccolo albero tipico di luoghi sassosi e rupestri, con fiori giallastri in      
pannocchie, le cui foglie e corteccia, ricche di tannino, si adoperano nella 
concia delle pelli (fam. Anacardiacee)

```

[the last part says: the leaves and bark, rich in tannin, are used in the tanning of leather.]


From sommacco to psammicco there is not too much distance.
But I agree that it is speculative.


Tannic acid is toxic, but the oral LD50 in rats is 2.26±0.083 g/kg body weight, so too much to hide in an *ostia*. 
However, that can be a writers license.


Tannic acid is a complex polyphenol with structure:


[![enter image description here](https://i.stack.imgur.com/dL6RQ.png)](https://i.stack.imgur.com/dL6RQ.png)


 10

The term ‘acido psammico’ is from the Greek and literally means an acid derived from sand, as @Alchimista explains in his answer. He argues that it could be a term for arsenic, and, although I do not think there is strong evidence for this, I think it fair to accept his answer, especially as my own answer is speculative. However, *for the record*, here it is.



> 
> I believe that *‘acido psammico’* is **not** a genuine Italian chemical (or psuedo-chemical) expression, nor a Sardinian dialect term, but a name invented by the author so that he could ascribe particular properties to the poison that suited his story.
> 
> 
> 


My reasons for thinking this is the term is used and recognized by a pharmacist, a doctor, a midwife, a priest and a professor of medicine. One would therefore expect it to have been in common use at the time and some record of it would have been found by an internet search or in the heavy-weight Italian dictionaries I have consulted. It is further understood by the daughter of a shepherd (although she, exceptionally had a formal education) in relation to tanning of hides, again suggesting wide general use not supported by any sources I have consulted.


The author of the book — Giorgio Todde — is still alive and there is an interview with him and a presentation by him on *YouTube*, so it may be possible to contact him and ask him directly. I will try to follow that avenue, with the help of colleagues with better written Italian, and update this answer if I have any successs.


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