Hello comrade, I want to tell you that all the methods described here do not give a normal result until you yourself find bumps on your forehead, you will receive a maximum of 30% yield. No one tells how to cook it correctly. But alas, I spoiled about 50 kg of Bk-4, bought false methods for $ 5,000 and we were deceived by giving a false method. Until this morning, I got yellow, then blue, then real crystals, but I found a way and now even without cleaning I got flour. I repeat, this product was not washed with a drop of solvent. And it was acidified with pure hydrochloric acid, I agree of course that it contains impurities, but what is the result)