herion comes from a plant, Ice come from people with less chemisty knowledge than me ( i have very little). It is make with lithiem, sulfuric acid, ani- ammonia and various degrees strenghs of ethidine.24 hours later a batch can be on the streets.
Heroin does NOT come directly from the plant. Among other things, the opium poppy contains morphine, codeine and thebaine (used to make oxycodone, buprenorphine etc). Heroin is normally made from morphine or codeine (through morphine intermediate), in a process that's COMPLETELY synthetic, making it little different to methamphetamine in this regard.
In the hands of the inexperienced or uneducated producer, either drug can be expected to contain undesirable side reaction products. The reason that meth is more prevalent (apart from current market demand) is simply due to the ease of obtaining the necessary chemicals. But make no mistake, the chemicals usually employed to turn codeine --> morphine --> heroin are very toxic, arguably more so than those normally employed to make meth. This is regardless of who does the synthesis or where it's performed.
In Australia, very little meth is manufactured using the lithium/ anhydrous ammonia process (known as birch reduction). According to Forensic reports it's nearly always made using chemicals available to certain industries and farming. Incidentally, no-one without a sound knowledge of the processes involved would attempt meth production using the Birch method. If conditions are not spot on, then BANG!! However, the product from Birch reduction is often claimed to be superior in quality, perhaps due most to the required expertise of the chemist.
As for sulphuric acid; it is frequently used to produce HCl gas (in preference to simply adding pool acid). Almost all mdma as well as other HCl salts would be made using HCl gas which was itself made from sulphuric acid.
Disregarding competence of the chemist, the problem with these drugs is not so much with the chemicals used. Sulphuric acid, lithium, ammonia etc etc are all used everyday in the production of pharmaceuticals and even some food stuffs; flavours, sweeteners, colours, etc etc. For example, Unless your vitamin C states "derived from natural sources" then it's undoubtedly been made via the old and trusted Hoffmann-La Roche 5 step process.
The simplified method of Vit C synthesis from glucose goes:
Glucose +H2/catalyst=Sorbitol
Sorbitol + acetobacter suboxydans--> Intermediate 1
Intermediate 1 + Acetone--> Intermediate 2
Intermediate 2 + Sodium Hypochlorite (bleach)-->
Intermediate 3 + HCl/ ethanol--> Ascorbic Acid (Vit C) in >90% yield
Like the chems used in Vit C production and other pharms, foodstuffs etc, it's the
purity that differs from those commonly employed in illicit drug production.
So until you see an authorised QC rating for heroin produced in Burma or where-ever, or you have access to analytical equipment, you can never be completely sure of the grade of chemicals that were used.