What is the Italian ‘Acido Psammico’ (Psammic acid?) I am reading an Italian detective novel — Lo stato delle anime by Giorgio Todde — 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…”
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), 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: