Here is a bit from a chemist.....


Ethanol is a hydrocarbon alcohol with 2 carbon atoms in its structure.

Isopropanol is a hydrocarbon alcohol with 3 carbon atoms in its structure.

Ethanol is the alcohol present in alcoholic beverages.

Isopropanol cannot be consumed.

70% of either means that the product contains 30% water and 70% alcohol.

Denatured means that some toxic compound has been added to the product to make it undrinkable.

90 or 95% for injection site prep means it is most commonly used to scrub off the skin prior to giving an injection. The higher concentration of alcohol more rapidly and effectively kills skin organisms. It also cleans off skin oils, dead skin, etc that are sources of contamination when the needle pokes the skin barrier.

Both alcohols are used for various skin rubbing/cleaning purposes, but "rubbing alcohol" is generally 70% isopropanol.

The 90 or 95% ethanol will burn better than the 70% alcohols.

90% == 180 proof
70% == 140 proof

Everclear is usually about 90% ethanol drinkable, and taxed...not enjoyable but drinkable. <img src="/images/graemlins/grin.gif" alt="" />

I will have to do some checking, but somewhere in the back of my mind I remember from one of my microbiology classes, that 70% alcohol had greater effectiveness as a bactericidal then 90+% alcohol. I am not sure I can find the reference, but will look around. I do know that a number of commercial disinfectants have narrow ranges at which they must be diluted for greatest cidal effect. More is not always better with disinfectants.

I looked our bottle of isopropyl alcohol at home and it was 91%. I also looked at a different brand of alcohol wipes and they were 70%.

The mystery continues. Pete

“Alcohol is a strong antiseptic (used to clean skin before injections). It works by coagulating the protein in bacteria. Pure alcohol simply forms a thin “skin” around the bacteria, but a 30% solution with water penetrates throughout & is more effective” www.RudimentsOFWisdom.com

"Disinfectants, which can be classified as high-, medium-, or low-level depending on the strength required, kill nearly all microbial life on objects or surfaces except for bacterial spores. "

"Antiseptics are used to inactivate or destroy organisms on skin or living tissue."

"Antiseptics are a diverse class of drugs which are applied to skin surfaces or mucous membranes for their anti-infective effects. This may be either bactericidal or bacteriostatic. Their uses include cleansing of skin and wound surfaces after injury, preparation of skin surfaces prior to injections or surgical procedures, and routine disinfection of the oral cavity as part of a program of oral hygiene. Antiseptics are also used for disinfection of inanimate objects, including instruments and furniture surfaces."

"Antiseptic, agent that kills or inhibits the growth of microorganisms on the external surfaces of the body. Antiseptics should generally be distinguished from drugs such as antibiotics that destroy microorganisms internally, and from disinfectants, which destroy microorganisms found on nonliving objects. Germicides include only those antiseptics that kill microorganisms. Some common antiseptics are alcohol, iodine, hydrogen peroxide, and boric acid. There is great variation in the ability of antiseptics to destroy microorganisms and in their effect on living tissue. For example, mercuric chloride is a powerful antiseptic, but it irritates delicate tissue. In contrast, silver nitrate kills fewer germs but can be used on the delicate tissues of the eyes and throat. There is also a great difference in the time required for different antiseptics to work. Iodine, one of the fastest-working antiseptics, kills bacteria within 30 sec. Other antiseptics have slower, more residual action. Since so much variability exists, systems have been devised for measuring the action of an antiseptic against certain standards. The bacteriostatic action of an antiseptic compared to that of phenol (under the same conditions and against the same microorganism) is known as its phenol coefficient. Joseph Lister was the first to employ the antiseptic phenol, or carbolic acid, in surgery, following the discovery by Louis Pasteur that microorganisms are the cause of infections. Modern surgical techniques for avoiding infection are founded on asepsis, the absence of pathogenic organisms. Sterilization is the chief means of achieving asepsis."
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2004, Columbia University Press.

"Isopropyl alcohol
Isopropyl alcohol or isopropanol is a common name for 2-propanol, an alcohol commonly used for application to the skin, and popularly referred to as rubbing alcohol. Its chemical structure is:

Its formula is C3H8O or more descriptively, CH3.CHOH.CH3.
The alcohol-based sterilizing swabs used to clean skin before injections typically contain a 30% solution of isopropanol in water.
Isopropyl alcohol is also commonly used as a cleaner and solvent in industry. It is also used as a gasoline additive for dissolving water or ice in fuel lines.
Boiling point: 83°C
Isopropyl alcohol, also known as isopropanol, is a colorless liquid with a pleasant odor. It is highly flammable. Isopropyl alcohol is found in alcohol sponges, cleaning agents, and rubbing alcohol (though some rubbing alcohols contain ethanol), and is a good disinfectant. Most rubbing alcohol contains 70% isopropyl alcohol. Poisoning can occur through skin absorption, oral ingestion, or inhalation. Symptoms from ingestion, inhalation or absorption of large quantities include flushing, headache, dizziness, mental depression, nausea, vomiting, anesthesia, and coma. Alcohol baths or sponges to soothe a fever can lead to acute poisoning through skin absorption or inhalation. Instead, the Regional Poison Center suggests using tepid water as a sponge bath to fight fever. "


There is considerable information on alcohol as a disinfectant/antiseptic. However, much of the information is not consistent from source to source. Some of the references refere to alcohol as disinfectant (not quoted), in others, as an antiseptic. From what I can find from a number of sources, at least 30% on up to an 85% solution seem to be referenced. Some of the sources point out that alcohol is not a really good disinfectant/antiseptic, in others, a good one. All of the sources that I could find, where a percentage of water is required, mention that water is necessary for the transport/absorption of the alcohol into the cell. Pete

Thanks! That is a very good link!