"Cage-like" Formazine particles, how are molecules arranged?

**Question:** What would the "cage-like" arrangement of Formazine molecules look like in a Formazine particle *while it is still suspended in water?* Would it be totally random, or have some kind of imperfect but recognizable regularity?


Formazine is used as an easily defined and prepared calibration or reference standard for turbidity measurements.


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


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


**above x2:** Formazine from [PubChem](https://pubchem.ncbi.nlm.nih.gov/compound/9602352#section=3D-Conformer).


From [Wikipedia](https://en.wikipedia.org/wiki/Formazine):



> 
> Formazine (formazin) is a heterocyclic polymer produced by reacting hexamethylenetetramine with hydrazine sulfate.
> 
> 
> The hexamethylenetetramine tetrahedral cage-like structure, similar to [adamantane](https://en.wikipedia.org/wiki/Adamantane), serve as molecular building block to form a tridimensional polymeric network.
> 
> 
> 


From [Formazine](https://www.photometer.com/en/GlossaryEntry/Formazine/):



> 
> The readings shown by turbidimeters are not scaled in the measured light intensity, but in concentration of a reference suspension. Because the accuracy of this calibration solution determines the reliability of subsequent turbidity measurements, it is of crucial importance.
> 
> 
> The internationally established turbidity standard for [calibration](https://www.photometer.com/en/GlossaryEntry/Formazine/) is formazine. This standard can be reproduced at any time with [the recipe](https://www.photometer.com/en/GlossaryEntry/?q=3.2%20Reagents) taken from [standard ISO 7027](https://www.photometer.com/en/GlossaryEntry/?q=Standard%20ISO%207027) (Water quality - Determination of turbidity).
> 
> 
> It is extremely important to observe the prescribed preparation temperature, because it affects the [particle size](https://www.photometer.com/en/GlossaryEntry/?q=Particle%20size) of the formazine particles perceptibly. The following Figure illustrates this. Errors caused by temperature variations are on the order of 1..2% per °C. Consequently, Sigrist keeps the preparation temperature constant to within ± 1°C.
> 
> 
> 


[![enter image description here](https://i.stack.imgur.com/i8dsN.jpg)](https://i.stack.imgur.com/i8dsN.jpg)


**above:** "Particle size distributions of formazine at various preparation temperatures" from [here](https://i.stack.imgur.com/i8dsN.jpg).


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


**above:** Enlarged from [TurbidityStandards](https://en.wikipedia.org/wiki/File:TurbidityStandards.jpg).


[![enter image description here](https://i.stack.imgur.com/EB9ksm.png)](https://i.stack.imgur.com/EB9ks.png)


**above:** Slide #10 from [What is Turbidity? John Daly, ISA NorCal President, South Fork Instruments, Inc.](http://www.isanorcal.org/download/tech2007_presentations/turbidity.pdf) Click for full size.




First, note that


* **formazine** structure attached from PubChem is a different compound;
* note that there are also, related, **formazan** $\ce{HN=N-CH=N-NH2}$ and “**formaldazine**” $\ce{CH2=N-N=CH2}$ (dimethylidenehydrazine);
* **formazin** (polymer) does not necessarily has to have cage-like structure, as this characterization belongs to hexamethylenetetramine in the quoted citation.


Hexamethylenetetramine (urotropine, $\ce{(CH2)6N4}$) can be prepared from formaldehyde and ammonia. In water it also somewhat decomposes to its precursors:


![Fig.1 - urotropine to/from formaldehyde and ammonia](https://i.stack.imgur.com/Fd2LO.png)


**Formazin** (also called **formalazine**) structure might be still unknown, as a related publication from 1976 states:[1]



> 
> … This substance, an insoluble condensation product of **uncertain composition**, is prepared by mixing solutions of hexamethylenetetramine and hydrazine sulfate. …
> 
> 
> 


Sometimes empirical-like formula $\ce{(C2H4N2)\_n}$ is claimed.[2]


Sometimes, claimed structure like following one is presented:[3,4]


![Fig.2 - claimed formazin structure w/ prep.](https://i.stack.imgur.com/cVDNC.png)


It was (with several other structures, less nice or likely), hypothesized (well, rather more complicated, with some ether linkages $\ce{-CH2-O-CH2\bond{-}}$ and $\ce{-NH\bond{-}}$ groups present), based on spectroscopic studies.[5,6]




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**References:**


1. Rice, E. W. [The preparation of formazin standards for nephelometry](https://doi.org/10.1016/S0003-2670(01)83146-9). *Analytica Chimica Acta* **1976**, *87* (1), 251–253.
2. Ziegler, A. [Issues Related to Use of Turbidity Measurements as a Surrogate for Suspended Sediment](https://water.usgs.gov/osw/techniques/TSS/ZieglerT.pdf). Turbidity and Other Sediment Surrogates Workshop; Reno, NV, USA, **2002**.
3. Kaur, N.; Kishore, D. [An Insight into Hexamethylenetetramine: A Versatile Reagent in Organic Synthesis](https://doi.org/10.1007/s13738-013-0260-2). *J. Iran. Chem. Soc.* **2013**, *10* (6), 1193–1228.
4. Sadar, M. J. [Stabilized Formazin Composition](https://patents.google.com/patent/US5777011A/en). US Patent 5,777,011, July **1998**.
5. Mashima, M. [The Infrared Absorption Spectra of the Condensation Products of Formaldehyde with Hydrazine](https://doi.org/10.1246/bcsj.39.504). *Bull. Chem. Soc. Jpn.* **1966**, *39* (3), 504–506.
6. Bondybey, V. E.; Nibler, J. W. [Infrared and Raman Spectra of Formaldazine](https://doi.org/10.1016/0584-8539(73)80094-7). *Spectrochimica Acta Part A: Molecular Spectroscopy* **1973**, *29* (4), 645–658.


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