Problem with qualitative analysis of possible copper(II)ion

Electrolysis of aqueous 1 mol/dm³ HCl with copper anode and graphite rod cathode was run for 10 minutes at 15 V. Blue-ish solution in the u-tube was obtained and put in a beaker for testing. 1 M NaOH (aq) was added but when the first drop was added, greenish precipitate was formed which quickly redissolved due to unreacted HCl. After many drops of NaOH solution turned yellowish-green cloudy precipitate-like solution. This was performed with fresh NaOH, yielding same result.

The expected compound was copper(II)hydroxide but no such blue solid was formed. Temperature of the solution was below 30 degrees Celsius which discloses the possibiltiy of copper(II)oxide being formed as copper(II)hydroxide decomposes after the heat. If someone here knows what is going on I will be happy to know!

I think Unionised is right. I happen to be doing something similar right now, and am just as confused by it as the OP. A few days ago, I dissolved half a teaspoon of salt (~2.5 cc, I know this is a lousy way to measure a loose powder, but I currently don't have a good way to weigh such small items) in 100ml of water. I dipped a piece of copper tubing into the solution as a consumable anode, and used a piece of copper wire as the cathode. 3.8v was applied. The current initially was about 250 mA, but that fell as corrosion built up on the anode. I only ran it intermittently, unplugging it during the night or when I needed the power supply for other things.

When sodium chloride is used instead of hydrochloric acid, the precipitates form during electrolysis. You might think of copper chloride and sodium hydroxide (or at least the constituent ions of these) being formed simultaneously in the cell, and then reacting.

Here is a picture, taken after power had been applied for a total of about 16 hours Note the layer of mostly orange precipitate, with some blue as well:



Here is a picture of the copper tube, covered in unknown copper compounds. By the time these two pictures were taken, this deposit had limited current to about 70 mA. Scraping it off restored the current to 250 mA:



I think I have both copper1 and copper2 compounds in the cell, but I'm just assuming that due to the colors visible. [urlhttp://webpages.charter.net/dawill/tmoranwms/Chem_Cu.html]this webpage[/url] says that electrolysis of copper in a chloride solution "precipitates CuOH, which being unstable autodehydrates to the yellow to orange Cu2O." This paper's abstract describes a similar formation of Cu2O with the hydroxide as an "intermediate". I suppose that could also account for the yellow stuff, if it's not the hydroxide itself.It does look a lot like the copper1 oxide shown at 3:17 in this video.

Whatever it is, this precipitate can be dried on paper without losing its yellow color. Since I'm doing this experiment to make black copper2 oxide, I am planning on heating most of the precipitate in air to dehydrate and oxidize it further.