Silver Nitrate Test for Acetylene gas qualification; looking for an appropriate instruction

Phosphine and Hydrogen sulfide along with some other hazardous gases are of impurities of acetylene plants witch are based on the reaction between water and calcium carbide. One of the simple and fast tests for ensuring that these impurities are less than the limit amount is the "Silver Nitrate test". The gas is allowed to react with the Silver nitrate solution for a specific time. Silver Sulfide and Silver Phosphide that are dark in color will precipitate and a visual inspection will suggest that phosphine or hydrogen sulfide have passed the limit or not.
I have found two Standards for Dissolved Acetylene that explain how to measure Phosphine and Hydrogen sulfide by this method. We've been acquiring the necessary equipment for this test. But actually I think their explanations are not adequate and clear and we have problems understanding the procedure.


At first, their instructions are the same while they use two different dimensions for the funnels. why? Second, they haven't written anything about the internal diameter of the stem of the funnel and the required amount of pressure that has to be adjusted. I think these are the most critical points in the amount of gas flow through the filter paper and so affect the result of the test and must be considered.
What is your suggestion?
In these two standards **only a **maximum amount**** of 3 psi is specified.
Can a plastic funnel(polypropylene) be used instead of glass?
Do you know any better standard for "dissolved acetylene" or other safer tests than the Silver Nitrate test? (**as it may form Silver acetylide which is explosive.**)


You can observe the specific pages relating to our discussion of those two standard below.
The IS308 Standard:
[![enter image description here](https://i.stack.imgur.com/m7mLi.jpg)](https://i.stack.imgur.com/m7mLi.jpg)
[![enter image description here](https://i.stack.imgur.com/iE7zh.jpg)](https://i.stack.imgur.com/iE7zh.jpg)
The BB-A-106C Standard:
[![enter image description here](https://i.stack.imgur.com/HvK8Y.jpg)](https://i.stack.imgur.com/HvK8Y.jpg)
[![enter image description here](https://i.stack.imgur.com/SkCBE.jpg)](https://i.stack.imgur.com/SkCBE.jpg)


Thanks very much




The full document can be see at [Archive.org](https://archive.org/details/gov.in.is.308.1988).


However, the standard technique is specified in an arbitrary *legal* document, and a responsible official of the Indian government would have to answer any question on deviation from that standard measurement procedure if used for *legal* purposes, e.g., showing in court that the concentration of acetylene exceeds a legal limit. "[P]ublication of the Bureau of Indian Standards... MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 11000... IS 308 (1988; Gases).


That said, for *practical* purposes, the pressure is limited to restrict flow rate and prevent damage to equipment. A plastic funnel *might* serve the purpose, if it could withstand the pressure and did not adsorb gases.


In short, if the purpose is to create a lab experiment or demonstration, any reasonable changes you make might be acceptable, but if this is to have any legal standing, the procedure should be followed *verbatim*.


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