WHAT IS INDEX AND HOW DOES IT WORK?

 

As embalmers, we have used the term “index” throughout our entire careers when referring to formaldehyde-based chemicals.  We refer to both arterials and cavities as 20 index, 30 index, and even 50 index, along with a wide variation of unique indexes in between. However, many embalmers can not tell you what these numbers mean.  For the most part, it is common practice for embalmers to refer to a stronger formaldehyde-based product when the index number is higher. 

Knowing our chemicals and what they are all about, as well as how they react to the tissue is imperative in becoming a successful embalmer.   We know that there are many different variations of chemicals put forth by an array of different manufactures used in the everyday preparation room.  One thing I can say for sure is that no two manufacturers are the same.  The industry used term “index” should follow the same guidelines that will allow the embalmer to make an educated decision on the scope of formaldehyde content contained in any one product. Majority of the chemicals us as embalmers use contain some form of preservative (for the purpose of this blog we will assume a formaldehyde-based product), dye, modifying agent (i.e., chelating agent), humectant, an organic salt, a wetting agent and some sort of solvent which is often water.  A simple arterial chemical can contain in excess of over 20 ingredients in order to achieve the desired results.  Chemistry can be complicated, even the slightest change in formulation can create an undesired result. 

When I was a student studying chemistry back in college, it was difficult for me to understand the need for an embalmer to know the purpose of the chemistry behind the products we used.  As I grew deeper into my career, it all began to make   much more sense to me. I realized that I could achieve better results when knowing how and why embalming products are made the way they are.  How solvents are used as vehicles to hold certain chemicals in suspension. How index has more meaning than being just a number. 

Index is just a professional term used in our profession that refers to the percentage of pure formaldehyde gas dissolved in 100ml solution. Formaldehyde is made up of 37% formaldehyde gas, stabilized using methanol (7-15%), with the remaining solution being made up of water (48-56%).   Methanol is used to hold the formaldehyde gas in suspension. If you were to take 100% pure formaldehyde solution as a volume then there is no space in solution to put any other chemicals into the mix, there simply would be no more room. Other chemicals are needed to stabilize the formaldehyde gas in suspension, whether that being water or alcohols like methanol.  100% pure formaldehyde is not possible, and some would say that is a 37% concentration of formaldehyde gas but a 100% index. The term “index” refers to the percentage of formaldehyde solution within the bottle. For example, take a look at a 25-index arterial chemical.  In truth, the 25 index represents 25 multiplied by the percentage of formaldehyde gas in solution (~37%), equalling (.25 x .37)100 = 9.25% true formaldehyde gas dissolved in our 16oz bottles.  If you use your algebra, we take 16 (bottle size) multiply by .25 index equals 4oz (or 25%) of formaldehyde solution in the bottle.   

When analyzing the formaldehyde content in an extremely strong cavity chemical such as Genelyn’s 16 oz Cavity Fifty +, a 50+ index, it would mean the 16oz bottle multiplied by .50 equals 8oz of that bottle is formaldehyde or formalin solution (Not formaldehyde Gas solution).  If you go by percentages like some regulatory services, they will take the 8oz (50% by volume) and multiply by 37% formaldehyde gas equalling 18.5% true formaldehyde gas. So now that we know how much formaldehyde gas is in the bottle, how do we relate that to how much formaldehyde is truly needed in order to properly embalm a body.

We know through studies that one ounce of 100% formaldehyde solution will combine with approximately 37 pounds of receptive body tissue. We also know that a 25-index arterial chemical contains 4oz of 100% formaldehyde solution. Therefore, it should be sufficient for approx.  148lbs of tissue (37lb x 4oz = 148).    However, with continuous injection and drainage methods, most of our solution flushes through the body.   This is one reason as to why we add additional chemicals and volume to our solution mix when embalming.  Volume is added to remove as many impurities (e.g., blood) from the vasculatory, capillary, and venous systems as possible, and to replace them with sufficient volumes of preservatives.   

The properties of formaldehyde are unique.  Formaldehyde acts as a great disinfectant and tissue stabilizer when used in sufficient quantities. Even if we use greater concentrations of formaldehyde from higher index chemicals, we still risk failing to preserve all tissues if our embalming methods are incorrect. Continuous flow or input of solution with continuous drainage can result in insufficient amounts of formaldehyde reaching all tissue areas (path of least resistance).  This can cause possible issues with stabilization of the tissues. 

Understanding “index” is extremely important for an embalmer to do their very best and be successful. Index, however, is just “one spoke in the wheel” of knowing your chemicals and how to make them work best for you and the families we serve.