The ability to detect the odor of a substance can be an important tool for the identification of that substance. Unfortunately, many odors are highly toxic or hazardous to the health of an individual and could cause chronic, detrimental effects to the respiratory system or even be fatal. Nowadays the odor of a substance is tested by indirect methods and at low concentrations.
The method you will be using is used only with substances known to be safe and which cause no harmful effects when inhaled; and are used to solely determine an odor sensitivity of substances that are safe to inhale. The substances used are food odors. The standard laboratory rules state that one should never inhale unknown chemical substances. Only the odor of a known substance could be determined for odor sensitivity if the following procedure is used. Hold the container 1 (one) foot away from the nose and gently waft the odor toward yourself with your hand.
Introduction:
In order to sell products today it has become necessary add pleasant, safe odors to the product. There also comes the point where someone must decide if they want to add another lemon smelling product when several competitors already have a lemon smelling product similar to yours on the market. This means either formulating new combinations of existing odors or synthesizing a new substance with a new odor.
Another important consequence is that a product may have an odor, which although not bad, you may want to mask by adding a substance that will neutralize the odor.
Threshold Odor Number (TON)
The TON is the number of times a chemical sample must be diluted using odor-free water so that its odor will be just detectable. The method used to determine the TON is the ASTM triangle method (American Society for Testing and Materials). The person testing for the odor is required to evaluate a group of three different containers, only one of which contains a substance that has an odor. The person doing the evaluation must take three precautions.
1. The person doing the evaluating should not start with a set of containers that has the highest concentration of the substance having an odor so as to avoid odor fatigue (where the nose becomes insensitive to the odor.
2. The person doing the evaluating must be working in a nearly odor-free atmosphere.
3. The person doing the evaluating must use odor-free soap when washing their hands.
You will not be determining a TON number but rather you will be identifying four types of odor. These will be an odor similar to cinnamon, an odor of vanilla, an odor of almonds, and an odor of bananas
Chemicals :
Vanillin solutions (0.10 %, 0.010 %, and 0.0010 %) [odor of vanilla];
Isopentyl acetate (0.10 %, 0.010 %, and 0.0010 %) [odor of bananas];
Trans-Cinnamaldehyde (0.10 %, 0.010 %, and 0.0010 %) [ odor of cinnamon]
Benzaldehyde (0.10 %, 0.01 %, 0.001 %) [odor of almonds]
Procedure:
Part I.
There are 13 sets of triangles to be tested. Each set contains three containers. Only one of the three containers has a compound that has an odor.
Obtain a triangle of containers. Test each one for an odor by holding the container 1 foot from your nose and gently waft the odor toward your nose. Remember only one of the containers holds a substance with an odor, the other two containers only have present distilled water. Take short, sharp sniffs of the sample to be sure that the odorant reaches the olfactory receptors that are high up in the nasal passages..
Select the container in the group (A, B, or C) that has an odor and in the box in the table on the data sheet record the odor (banana, cinnamon, almond or vanilla) and record a relative intensity ( 1 = a very faint odor, 2 = a faint odor, 3 = an easily noticeable odor,
4 = a strong odor, 5 = a very strong odor ) next to the name of the odor. In the other two boxes you should place a 0 to indicate no odor.
Example:
| Bottle Set | Bottle A | Bottle B | Bottle C |
| 1 | 0 | 0 | Acetophenone = 3 |
You should wait a few minutes between examining each of the bottle sets so as to allow any possible nose fatigue to pass or diminish.
Please be sure that you replace the bottle caps after you finish the bottle set. Do NOT discard or dump any of the solutions in the bottles.
Part II
Obtain 20.0 mL of 0.100 % acetic acid (odor of vinegar) and place it in a 400 mL beaker. Test it by the method above and determine if you detect an odor. If you do, add 20.0 mL of water and stir the mixture (remember to stir the solution after each dilution). You will have added an equal amount of water as the original 0.100 % solution. This cuts the percentage in half; you now have a 0.0500 % solution. Again test it to see if you can detect the odor. If you can't, then you have reached the maximum dilution; if you still can detect an odor, then add 40.0 mL water, which again doubles the total volume and cuts the percentage in half again. You now have a solution that is 0.0250 %. Repeat the procedure. If you still detect an odor do another dilution by doubling the total volume again which gives you half the percentage, 0.0125 %. If you still detect an odor do one last dilution to 0.00625 %.