This experiment concerns an easy way to determine the concentration of hemoglobin in blood, and by extension to detect anemia. Hemoglobin is the red pigment in red blood cells, and the chemical that allows the cells to transport oxygen to the tissues; if there is not enough hemoglobin present in the blood, the patient will feel weak, and become winded easily by exertion. The fastest, and one of the simplest ways of determining the concentration of hemoglobin in the blood is by the method developed by Tallquist (also seen sometimes as Tallqvist), a finnish engineer, around the turn of the century. This test takes advantage of the fact that hemoglobin is strongly colored, and fluids containing more or less of it will have different colors. A drop of blood is obtained from the patient and placed onto absorbent paper, then its color is compared with a color chart. In practice this gives hemoglobin concentrations to within ten to twenty percent, depending on the skill of the operator in comparing color. I will show how to use a commercial Tallquist scale, and how to replicate that scale using commonly available and inexpensive materials.
Standard disclaimer/bio-hazard disclaimer: This experiment and others in this section concern the biology of the human body. As well as dangers from heat, sharp tools, electricity, and chemicals as mentioned in other demos, this project may involve exposure to materials such as blood, urine, saliva, or other potentially infectious materials. Before duplicating this experiment, it is your responsibility to familiarize yourself with the necessary precautions for safely handling such material. Only a brief overview of any safety precautions can be given here; the rest is up to you. As I am not present to hold your hand, I can take no responsibility for your safety when engaged in potentially dangerous activities.
I bought my tallquist scale from Ward's Biological Supply. I would not recommend them, as I have literally never managed to order from them without something about the order needing to be fixed. While they're one of the largest suppliers and no doubt do a great job of supplying schools and universities, I feel they do a very poor job with small orders and have no use at all for individuals, amateurs, and tinkerers. Searching the internet for 'tallquist scale' will turn up many suppliers. Some of the ones aimed at home schooling might be more friendly to individuals.
The Tallquist scale I purchased came as a loose and flimsy sheet of printed paper, and a bundle of filter paper scraps in a plastic baggie. I took the scale to an office supply and had it laminated in clear plastic before using it. Without something to protect it from exposure to blood, the scale would quickly get soiled and could not be cleaned. With its clear plastic coating, any blood that gets on it can be cleaned off with alcohol.
You'll want to get your supplies in place before you lance yourself or your patient. Get an alcohol wipe ready, select a lancet and place it in your lancing device, and get a piece of absorbent paper ready. Set the scale where you can reach it quickly; you'll have a short window of time in which the color of the blood will correspond to the scale.
Clean the finger you intend to lance with the alcohol pad. After you've cleaned it, wait a few seconds until the alcohol dries. Not only does the alcohol lower the surface tension of the blood and prevent it from forming a drop, it increases the pain of the puncture and the lancet will carry some into the cut. For the least painful puncture, you will want to puncture the fingertip along the side.
Once you've punctured the finger, you will have to make a drop of blood to test. Squeeze the finger to 'milk' blood down towards the tip until you have a drop about 1/4 inch in diameter. Place the absorbent paper over the drop and let the blood slowly absorb. If you have enough blood in the drop, the spot on the filter paper will be at least 1/4 inch in diameter on the opposite side from where the blood is added. If the drop absorbs too quickly the spot will be irregular in color; ideally the spot is uniform in color without any light or dark areas. If it has places that are light, squeeze the finger again and add more blood. Initially the blood spot will appear shiny and wet. At the moment that the blood spot stops appearing shiny you can compare it with the scale. You can continue comparing colors until the blood drop begins to appear dry; at that point it will darken and give a false result. For the most accurate result, compare the colors from one end of the scale to the other, noting where the color of the scale matches the color of the blood, then repeat beginning from the opposite end of the scale. If you find that you are matching the blood spot's color at different points on the scale when beginning from different ends, the true color is probably midway between the points.
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