What Is "PPM"?
The ppm is an acronym for "parts per million", a unit of measure that describes how much of one substance (called the "solute") is dissolved in a sample of water (called the "solvent"). This is a measurement of concentration (or density), which can often be helpful in our daily lives. The ppm can be used to measure the concentration of many substances, such as the minerals in our drinking water or the oxygen in a fish aquarium. Although the ppm is commonly used for concentration measurements, it only provides us with a ratio of the solute's mass to the mass of the water, without specifying the water’s total volume. But, more often we need to know the total amount of solute dissolved in the water. This is important, for example, when determining the therapeutic dose for a medicine or the ingested level of a toxin. Without including the size of the container we are testing, which tells us the amount of water our solute is dissolved in, the ppm ratio by itself does not tell us how much solute the water contains. To convey this information, scientists use a more appropriate unit of measure, one which specifies the solute’s concentration in units of “mass per unit volume”. The unit commonly used is the "milligram per liter", abbreviated mg/L. The mg/L always references the solute’s mass relative to a fixed volume, one liter.
Note: Frequently, the ppb (parts per billion) is used to measure solute concentration. Although not specifically addressed here, 1 ppm = 1000 ppb.
In the above example, each of the containers will measure the same concentration of H2, 1 mg/L (10 drops of H2Blue). But, these three containers do not contain the same amount of dissolved H2. This is because, as the volume of water is halved, so too is the amount of dissolved H2, resulting in the same concentration and the same ppm reading in each container. From this example, it can be seen that the mg/L measurement does not indicate how much H2 will be ingested when drinking the contents of each container. In order to determine how much H2 will be ingested, the mg/L measurement obtained from the test sample must be referenced to the volume of water. This means that we must calculate the equivalent concentration of each container if that same amount of H2 was dissolved in 1 liter. For example, glass #2 (1/2 liter), which measures 1mg/L and contains 1/2 mg H2, in fact has an equivalent concentration of 0.5 mg/L (1/2mg of H2 dissolved in 1 liter = 0.5 mg/L). Based on this principle, you will ingest the following amounts of H2 if you drink the entire contents of each of the above containers, all of which measure 1mg/L:
Glass #1 (volume = 1 Liter): 1 milligram of H2 will be ingested
Glass #2 (volume = 1/2 Liter): 1/2 milligram of H2 will be ingested
Glass #3 (volume = 1/4 Liter): 1/4 milligram of H2 will be ingested
As a consequence, even though all three glasses measure 1 mg/L, only glass #1 will deliver 1 mg of H2 when the entire container is consumed.
The ppm is a unit of measurement which provides a ratio of the amount of a dissolved substance to the amount of water it is dissolved in. Therefore, 1 milligram of a substance dissolved in 1 million milligrams of water will have a concentration of “1 part per million”. Because 1 liter of water weighs 1 million milligrams, 1 part per million is also the same as 1 milligram per liter when referenced to a volume of one liter. Because flow-through type devices are generally capable of producing a liter or more at the same H2 concentration, the mg/L reading of a test sample will be representative of the number of milligrams of H2 we will ingest if we drink one liter. When interpreting the mg/L measurement from a sample of H2 water produced by technologies other than flow-through type devices (tablets, sticks, cartridges, etc.), the ppm measurement must be converted to mg/L by adjusting it to the volume of H2 water being sampled. Only by performing this conversion can we determine how much H2 we will ingest when drinking the entire contents of the sampled container.
The information about parts per million contained on this page is also available for download in PDF format here (rev 2.6):
Passive (non-electric) flow-through countertop devices:
There are flow-though devices available which produce H2 water without electricity, utilizing magnesium similar to the tablets. These devices connect to the faucet with a simple diverter, supply H2 water on demand, and can produce a respectable concentration of H2 water (1ppm or more). But, while electric flow-through devices previously described can produce essentially as much H2 water as the user wants, these passive devices must permit the water inside their chamber to remain in contact with the magnesium for a certain amount of time in order to produce and dissolve the H2 gas into the water. Therefore, they can only produce about two liters of H2 water at the rated concentration before needing to "regenerate". After regenerating, the cycle can be repeated. The amount time varies with device, source water, etc. As long as this type of device can produce at least one liter of water at the sample concentration, then the concentration of the H2 water it produces can be evaluated in the same way as electric flow-through devices described previously.
From Table 3 it can be seen that, as the dissolved H2 concentration falls below 1 mg/L, the amount of water which must be consumed to deliver 2 mg/day of ingested H2 becomes prohibitively high. For example, at a concentration of 0.2 mg/L, you must consume 10 liters in order to ingest 2mg of H2. Therefore, to avoid having to consume large (and possibly unhealthy) amounts of water, it is important to choose a device or technology which is capable of consistently delivering H2 water at or above approximately 1 mg/L.
How to use this table:
* Decide how many milligrams of magnesium your tablet contains, usually found on the label (if using two tablets, double the results shown in columns 3, 4 & 5). The left side of the table corresponds to 50 mg and the right side corresponds to 80mg.
Note: Some tablet labels will indicate both the magnesium amounts (typically 50-80 mg), as well as the weight of the tablet itself (typically in the 500 mg range). Be sure to use only the magnesium weight, not the weight of the entire tablet!
* Select the value in column 1 corresponding to the volume of water into which the tablet is to be dissolved.
* Select the value in column 2 corresponding to the anticipated percentage of dissolved hydrogen. Values will vary depending on preparation method and other factors, but will typically be in the 25% to 75% range, depending on the production methodology.
* Column 3 shows the approximate ppm you would expect to measure in the test sample based upon the amount of magnesium in the tablet, container volume, and % of the produced H2 which actually dissolves into the water.
* Column 4 shows the equivalent mg/L after adjusting the volume to one liter.
* Column 5 shows the approximate amount of H2 which will be ingested if one drinks the entire contents of the container as listed in column 1.
Notice that for any given tablet and dissolved H2 %, while the measured ppm's change with container volume, the ingested H2 amounts do not!
Example: One 50 mg tablet is capable of producing 4.2 mg of H2. If it is placed into a 500mL container, and we assume that 50% of the H2 gas produced will dissolve into the water (with the remaining 50% escaping into the air), then a concentration of approximately 4.2 mg/L will be measured, and approximately 2.1mg of H2 will be ingested when consuming the entire 500 mL of tablet water.
How are ppm and mg/L related?
We can think of 1 ppm as "1 part of a substance (solute) dissolved in 1 million parts of a solution" (in our case the solute is H2, hydrogen gas and the solution is water). So, what is a "part"? "Part" represents a unit of measure, in our case the "milligram" (mg). Therefore, 1 milligram of H2 ("1 part") dissolved in 1 million milligrams of water ("1 million parts") is "one part per million". And, since 1 liter of water happens to weigh 1 million milligrams, 1 ppm is equal to 1 mg/L (for dilute concentrations).
Note: This is only true when comparing units of mass, not when comparing volumes, # of moles, or # of molecules.
Figure 2 shows three glasses, each of which contains the same amount of water, 1 liter, and also the same three amounts of dissolved H2 as in Figure 1, 1 mg, 0.5 mg & 0.25 mg. In contrast to Figure 1, they will now each measure different concentrations of H2, 1 mg/L, 0.5 mg/L and 0.25 mg/L respectively. Just as in Figure 1, the three glasses in this example do not contain the same amount of dissolved H2. And, because their concentrations are different, drinking the entire contents of each glass WILL NOT provide the same levels of ingested H2. In order to receive the same ingested amounts of H2, you will need to drink varying amounts of each as follows:
Glass #1: You must drink 1 liter of 1 mg/L water to ingest 1 milligram of H2
Glass #2: You must drink 2 liters of 0.5 mg/L water to ingest 1 milligram of H2
Glass #3: You must drink 4 liters of 0.25 mg/L water to ingest 1 milligram of H2
From this example, it can be seen that when the mg/L measurement is referenced to a volume of 1 liter (expressed in terms of "mg/L"), the mg/L reading DOES indicate how much H2 will be ingested if you drinking 1 liter from each container.
How much H2 do I need?
Now that we understand how to calculate the amount of hydrogen gas contained within a particular volume using the concentration measurement, the question often asked is,
"How much H2 do I need to ingest everyday"?
Scientists are asking the same question, and the answer is currently being researched. What we do know is that human studies show significant health benefits when participants consume hydrogen water daily with concentrations in the 1-3 mg/L range. This gives us a "target" dosage of approximately 2 mg/day. Therefore, if your water has a concentration of 1mg/L, then, by consuming two liters per day, you will ingest 2 mg of H2 per day. Based upon the H2 concentration of your water, you can use Table 3 below to calculate the volume of water you should drink in order to ingest approximately 2 mg of H2 per day.
Interpreting the results of the ppm measurement for batch-type electric devices:
Because batch devices contain a fixed volume of water into which the H2 gas is introduced (they range from 250 mL to 2 L or more), they are, in terms of ppm interpretation, more like tablets, which also introduce the H2 gas into a fixed volume of water. Because they produce H2 gas electrically, they are not restricted in the amount of H2 gas they can produce, but the total dissolved H2 levels are influenced by the same variables mentioned previously. To interpret the ppm results from batch-type devices, use Table 2 in the previous section with the volume and concentration values which most closely match yours, or use the method below.
As you can see in Figure 4, the same amount of H2 gas dissolved in a smaller volume of water will give a higher ppm/ppb reading. That is because ppm/ppb readings are not measurements only of mass (milligrams), but of mass per unit volume (milligrams per liter). Therefore, both the dissolved mass and the volume of water in which that mass is dissolved must be considered. Also, although not discussed here, other variables, such as increasing the run time of a single session (if adjustable), or running the device for multiple consecutive sessions, can have a large impact on dissolved H2 levels. Therefore, when comparing the dissolved H2 performance levels of different devices, make sure that parameters such as water volume and run time are the same.
A simple method for determining H2 amount:
If you want to use the mg/L measurement to calculate the amount of dissolved H2 in any size container, here is a simple method: Multiply the measured mg/L by the size of the container the sample was taken from (in liters). This will tell you how much H2 is contained within the container, and how much H2 you will consume if you drink the entire contents.
For Example: If you have a 500mL portable bottle (0.5L) which produces H2 water at a concentration of 2 mg/L, multiply: 0.5 L x 2 mg/L = 1 milligram H2. Therefore, if you drink the entire 500 mL container, you will ingest 1mg of H2.
The following example will help to illustrate why the mg/L measurement alone cannot tell us how much dissolved H2 a sample of water contains. Figure 3 shows the results of dissolving 1 milligram of H2 into three different volumes of water, 1 liter, ½ liter, and ¼ liter.
If the same amount of H2 gas is dissolved into half the volume of water, the measured ppm (H2 concentration) will double. But, this does not mean that the amount of dissolved H2 has doubled-in fact, the amount of H2has remained the same. Therefore, as we have seen in these examples, to know how much H2 will be consumed, the mg/L measurement must take into account how much water we have at that concentration.
Just to give some perspective on the relationship between mg/L and volume, consider the 6 mL sample of water used when testing H2 concentration with a reagent. Because the volume is so small (0.006 liters), it takes only 6 μgrams (6 millionths of a gram) of dissolved H2 in 6mL of water to produce a concentration equivalent to 1 ppm!
In light of our explanation about ppm's and water volume, the following example shows how unscrupulous marketers of batch-type devices can claim a significantly higher ppm/ppb measurement by simply reducing the amount of water used in a device (ppb = parts per billion; 1 ppm = 1000 ppb).
Hydrogen water produced using electric devices, such as alkaline ionizers and hydrogen infusion machines (HIM's):
Alkaline ionizers produce hydrogen water by reducing (adding electrons to) protons in the water (H+ ions). The reduction reaction produces hydrogen gas bubbles (H2) at the cathode:
The turbulent flow of the water across the cathode(s) then helps to dissolve the H2 gas bubbles into the drinking water.
Recently, a new type of hydrogen water device has emerged on the market, the hydrogen infusion machine (HIM). This type of device does not have the same type of chamber as a conventional electrolyzer, and instead produces H2 gas in a small hydrogen gas chamber (using a proton-exchange membrane containing solid polymer electrolyte, PEM/SPE). Then, rather than depending only on turbulent flow to dissolve the gas into the water, mixes the H2 gas into the drinking water stream using a special "dissolver chamber". Because this class of device utilizes specialized electrically-conductive membranes tightly sandwiched between the anode & cathode, the source water need not contain any level of minerals (TDS), and in fact can produce H2 water even with distilled or RO water sources. While it is commonly referred to as a "neutral-pH device", the H2 water produced by an HIM will not necessarily be "neutral"; the final pH will be determined by the pH of the source water, which it typically does not alter.
Some companies have improved upon the performance of the HIM by adding a "pressure chamber". These chambers use pumps to place the hydrogen water and gas under high pressure. The addition of pressure improves the ability of H2 gas to dissolve according to Henry's Law. t the present time, H2 concentrations in the 3-4 mg/L range are typical. As designers increase the pressure levels in these units, you can expect to see dissolved H2 concentrations in the 7-10 mg/L (or more) range!
Another type of electric device now being marketed for producing H2 drinking water is the hydrogen pitcher, and its smaller counterpart, the portable hydrogen bottle. These are “batch” devices (not flow-through), which typically (but not always) use PEM/SPE membrane technology to produce neutral-pH H2 water. The levels of dissolved H2 will vary based on run times and water volumes. Because their run times are typically in the 5 to 15 minute range, they do not have the capacity to produce the same volume of water per minute as flow-through devices, although they are capable of producing H2 water with comparable ppm’s.
Note: Some batch devices utilize electrodes without membranes (not PEM/SPE), commonly referred to as "Brown's Gas" devices. Because there is no membrane to isolate anodic and cathodic products, the mixing of H+ and OH- ions tend to cancel out any change in pH that would otherwise occur. Therefore, while they typically produce water which is close to the source water's pH, they may also add unwanted byproducts into the drinking water, such as chlorine or ozone gas.
Interpreting the results of the ppm measurement for electric flow-through devices
Hydrogen tablets contain a finite amount of magnesium, and therefore can only produce a finite amount of hydrogen gas. They are also placed into a finite amount of water, which dictates (along with other variables) the maximum ppm’s which can be measured. But, electric flow-through devices have no such limitation, and therefore essentially have an unlimited supply of electrons for producing H2 gas (at least, as long as there is power available), as well as an unlimited supply of water. As a consequence, we need not be concerned with the container size from which the 6 mL test sample is taken when interpreting the ppm's measured using H2Blue. We know that, since electric flow-through devices can produce H2 water continuously, any test sample taken directly from the machine will likely be representative of its ability to provide any volume of H2 water at that concentration (within the design constraints of the machine). Therefore, to determine how much H2 we will ingest, we only need to know two things:
1) The H2 concentration (mg/L) of the water it produces;
2) The total volume of H2 water consumed (liters).
Table 2 shows the amount of H2 that will be ingested (in mg) when drinking 3 different volumes of hydrogen water, 250 mL, 500 mL and 1000 mL (1 liter), each one calculated for six different H2 concentrations, 0.1 to 5 mg/L:
Calculating the theoretical maximum amounts of H2 which can be produced and dissolved when using magnesium tablets:
Knowing the number of milligrams of elemental magnesium contained in the tablet (not the mass of the whole tablet, which can be much greater), we can calculate the theoretical maximum amount of H2 which can be produced. Then, knowing the maximum amount of H2 gas which can be produced, we can also approximate the levels of dissolved H2 (mg/L) and ingestible H2 (mg) which can be expected based upon using some reasonable values for production and dissolving efficiencies. When calculating ingested H2 levels, it is important to remember that we are only considering dissolved H2 gas, not the amount of H2 produced. This is because in any system, a considerable amount of the H2 gas produced may never dissolve into the water, and instead escape into the surrounding air. While visible undissolved or “suspended” H2 gas bubbles may also be of some benefit (if you can ingest them before they escape), it is more difficult to quantify their amount (and therefore the contribution they make to total ingested H2) using conventional methods such as titration.
A few variables come into play which have an impact on the percentage of H2 gas produced which ultimately dissolves into the water. For any given tablet size, these variables include:
* Whether the container is open or sealed: - pressure can help H2 dissolve better, although some tablets may perform better in an open container.
* Materials from which the container is constructed - less-porous materials hold H2 better
* The amount of time the tablet is permitted to dissolve - more time is generally (although not necessarily) better than less time.
* The temperature of the water - H2 gas will dissolve better in cold water, but the reaction will proceed slower
* The size of the magnesium particles- Smaller magnesium particles can result in smaller, "more dissolvable" H2 gas bubbles
*Agitation -Shaking or mixing the contents can encourage more H2 gas to dissolve
While a larger container may produce lower ppm readings, the amount of ingestible H2 will not necessarily be less.
Table 1 shows the maximum possible H2 production, measured ppm's, equivalent mg/L's, and ingestible H2 one can expect, for two different magnesium tablets (A & B). Four different volumes of water and four percentages of dissolved H2 are also listed.
What does the measurement tell me about my hydrogen water?
When using H2Blue to measure a sample of hydrogen water, each drop represents 0.1mg/L of dissolved H2 gas. By adding together the total number of drops required to reach the titration endpoint (the point at which the next drop does not turn clear, but remains blue), the dissolved H2 level in the sample can be calculated (see Technical page). Because the results of each measurement done with H2Blue are expressed in mg/L, it is important to understand how the measurement tells us how much H2 is in our water. What we really want to know is "how much hydrogen will I ingest if I drink the entire contents of the container from which the test sample was taken"? How the results are interpreted depends, in part, upon how the hydrogen water was originally produced.
Hydrogen water produced using hydrogen tablets:
Hydrogen tablets produce hydrogen gas through the reaction between elemental magnesium (Mg) and water:
The production of hydrogen gas bubbles can easily be observed when placing a tablet in a clear container. If the tablet is placed into a sealed container, the pressure will rise as the volume of H2 gas produced increases. The elevated pressure can help the H2 to dissolve, although too much pressure may attenunate the reaction.
Distinguishing between "produced" and "dissolved" hydrogen gas:
Because each tablet contains a fixed amount of magnesium metal, usually in the range of 50 to 80 milligrams, the total amount of H2 gas which can be produced from each tablet is also fixed. Although the theoretical maximum amount of H2 gas which can be produced from one tablet (under ideal conditions) can be calculated based upon the amount of magnesium in the tablet (usually indicated on the label), not all of the H2 gas which can be produced will be produced because 1) some magnesium will react while still in the package due to exposure to environmental water vapor (humidity); 2) not all of the magnesium contained within the tablet will necessarily react when placed into water because of the formation of oxides on the magnesium particles (passivation).
Regardless of how much H2 is produced, not all of it will dissolve into the water. This is because a portion of the gas will escape into the air and be wasted. The percentage of H2 produced which actually dissolves into the water is typically in the 25% to 75% range. This percentage can be influenced (and often improved upon) by altering tablet variables such as magnesium particle shape & size, and acid content, as well as environmental variables such as temperature, reaction time, and pressure.
Calculating the amount of ingestible H2 based on the mg/L concentration:
In order to convert the mg/L measurement to the amount of ingestible dissolved H2 gas, the size of the container into which the tablet is placed (and from which the 6ml test sample is taken) must be taken into consideration. This is because it takes fewer milligrams of H2 to produce 1 mg/L in a smaller amount of water than it does in a larger volume of water. The graphic in Figure 1 illustrates this concept: