The formula you show is for Copper (II) Nitrate Hydrate. That is bad stuff. See pdf attached. The benefit to sewer systems is not in the processing of sewage or quality of the effluent water, but is beneficial to to operator and/or homeowner who has roots infiltrating his pipes. Some use sulfuric acid for the same function. Neither belongs in the effluent of the sewer system on a steady basis.
Your reference to one application of the cupric nitrate is as part of a rocket fuel. Of course, that is because it is a powerful oxidizer. I am glad I looked at the MSDS. It is one thing to buy highly concentrated Hydrogen Peroxide, knowing it is a powerful oxidizer, and having a label that says so, it is another to dry out the residue from your etch tanks and be left unaware that you have just made the same type of material. It doesn't come with a label. Thanks for the heads up.
The term dilute Nitric acid is relatively meaningless. Unless the concentration is specified, I would not know what to order from a chemical supplier. If I have to buy concentrated Nitric acid and experiment to make the required concentration, that is a step I prefer to avoid. I much prefer the pool acid I can buy at HD, 2 gals for approx $10, and that I keep for use in my pool. This comes in a concentration of 14-15% (concentrated is 35-38%), is cheap and available without special shipping precautions. During the course of my career, I have handled concentrated Hydrochloric, Sulfuric, Nitric, Hydrofluoric and Acetic acids. Some of them in combination at high temperatures. This was always done under a fume hood with gloves thick enough to make picking up small things very difficult. There were occasional spills and cleanups, all contained within the equipment, and I still have all my fingers and toes, both eyes work, and no acid burns on my body. Yes, you can get very hurt by the 15% pool acid, but some care, common sense and preparation goes a long way to mitigating the probability of such an occurrence.
I don't think we need to get into a full blown discussion about this. We each have our like and dislikes, and we should agree to disagree.
(Another) Harvey
I do RF PCBs requiring micro strips etc. It must use double sided FR4 boards with consistent permittivity and very accurate trace thicknesses for impedance matching or inductance chokes.
The hackaday technique assures such results repeatably.
All acids must be handled properly, I have 30 years experience with conc. NITRIC and never a problem. HCL is also dangerous, fumes, and can emit large volumes of chlorine if it comes into contact with household ammonia cleaners.
http://www.flinnsci.com/media/396140/acidsafety.pdf
When nitric is etching copper it bubbles a bit and self stirs the mix for cleaner trace edges I have found. Also the fine even bubble generation reveals any improperly cleaned copper areas within a couple seconds. Such areas can lead to longer immersion times which will cause over etching of the properly cleaned areas. In effect it gives me quality control feedback that other etchants don't.
Further, the copper nitrate end product is beneficial to sewer systems for restricting root growth, a fungicide or as a soak for preserving outdoor wooden surfaces.
- Cupric Nitrate (Copper Nitrate) Cu(NO3)2·nH2O, green powder or blue crystals which is soluble in water; used in electroplating copper on iron; as a catalyst and nitrating agent in organic reactions; component in rocket fuel; fungicides and wood preservatives; textile dyeing and printing; pigment in ceramics;