Last weekend, wanting to eradicate undesirable weeds that invade our terrace, I went to a gardening centre to buy an herbicide; I accept the fact that dandelion be part of our lawn's ecological balance but refuse to see it invade the patio. On the other hand, concerned to use a weed killer without any toxicity for humans and animals when applied, and which doesn't leave any toxic residue in the environment, I wanted a so called ecological product. The one recommended by the merchant satisfied these criteria; its label mentioned the active element, acetic acid, in a proportion of 62,5 g per litre. I figured that it was an acetic acid solution a little more concentrated than vinegar. I thus bought a one litre spray bottle costing of 7,97 $ Can.
I applied the product; there was indeed a strong vinegar odour. I must admit its effectiveness; after an hour or two, the plants already started to desiccate. On the other hand, curiosity pushed me to search the Internet; I learned that commercial vinegar was usually a 5% acetic acid solution, that is to say 1,01 g per millilitre, therefore 101 g per litre. Vinegar sold in grocery stores is thus a solution 1,6 TIMES more CONCENTRATED than the product I bought. Pursuing my investigation further, I consulted the manufacturer's Web site; the detailed descriptive product leaflet indeed mentions as active ingredients acetic acid mainly (5-10 Wt.%), and in a lesser proportion, citric acid (3-7 Wt.%).
I was surprised, indeed shocked. Would it be a less concentrated solution of vinegar to which a small amount of citric acid was added? Save that the presence of a small proportion of lemon juice is the key of the effectiveness of this product? Being neither a chemist, nor a horticulturist, I cannot pass judgement with certainty on this question. On the other hand, if such is NOT the case, perhaps I was swindled! I bought vinegar at 7,97 $ Can. a litre, when I could have bought 4 litres for 2,59 $ Can. in a supermarket (Loblaws, «no name» brand)! I hate to admit this, but I fear this may be the case. The Agricultural Research Service of the United States Department of Agriculture has tested vinegar, including the household variety, as a weed killer; you can read the results for yourself.
Ecological products are popular. Motivated by easy and quick profit, several companies undoubtedly will try to exploit the consumer with various «environmentally safe» products whose effectiveness is doubtful, or which could be replaced by inexpensive solutions.
Once again, the Latin expression «Caveat emptor», buyer beware, makes a lot of sense. I would very much like that people who have precise information concerning the product mentioned, or ecological products in general, post this information on the blog.