### Measuring Density Using “Archimedes Principle”

Article #3- By Ami Gur-May 30 2024

** Welcome back** to “Precious Metals Mechanics by Ami Gur.” In our

last post, we explored how to measure dimensions with a caliper to calculate the volume of precious metal items like bars and coins. Today, we’re taking another step forward by discussing how to measure the density of these items using Archimedes’ Principle. This method is a valuable tool for verifying the authenticity of precious metals, and best of all, it can be done without any special equipment.

**What is Archimedes’ Principle ?**

Archimedes’ Principle states that when an object is submerged in a fluid, it experiences a buoyant force equal to the weight of the fluid displaced by the object. This principle is fundamental in measuring density because it allows us to determine the volume of an irregularly shaped object by observing how much water it displaces.

**Why Measure Density ?**

Density is a characteristic property of materials, including precious metals. Each metal has a unique density, and by measuring the density of an item, we can compare it to the known densities of pure metals to confirm authenticity. For example, the density of gold is 19.32 g/cm³, while silver has a density of 10.49 g/cm³. Significant deviations from these values can indicate impurities or counterfeit items.

**How to Measure Density Using Archimedes Principle ?**

Here’s a step-by-step guide to measuring the density of your precious metal items using Archimedes’ Principle:

**Materials Needed:**

– A container of water (large enough to fully submerge your item)

– A scale (preferably one that can measure to at least 0.01 grams)

– A thin thread or lightweight string

– A ruler or measuring tape (for additional measurements if necessary)

**Step-by-Step Instructions:**

**Weigh the Item**: Use the scale to measure the weight ofyour item in grams. Record this value (W1).

**Prepare the Container**: Fill the container with enough water to completely submerge the item. Ensure the container is on a stable surface to prevent spills or inaccurate measurements.

**Calibrate the Scale with the Container**: Place the container ofwater on the scale and calibrate it to zero. This ensures that the weight of the container and water is not included in your measurements.

**Submerge the Item**: Use the string to hold the object and immerse it in the water, making sure it is not touching the bottomor the sides of the container.

**Measure the Displaced Water**: The weight in grams shown on the display of the scale is the actual volume of the item in cubic centimeters (cm³). This is because the volume of water displaced is equal to the volume of the item.

**Calculate the Density**: Now that we have both the weight and the volume, we can easily calculate the density using the formula:

**Compare Densities**: Finally, compare the theoretical density of the metal (e.g., 1**9.32 g/cm³**for gold,**10.49 g/cm³**for silver) with the density you calculated. Significant deviations can indicate impurities or counterfeit items.

**Example Calculation**

Suppose you have a silver ingot that weighs **500.64** grams (W1). After submerging the ingot in water, the scale shows **47.54** grams of water displaced, which is the volume of the ingot in cubic centimeters.

Using the formula for density:

Density =W/V={500.64}/{47.54} = **10.53** { **g/cm³**}

Comparing this to the known density of silver (**10.49** g/cm³), we can confirm that the ingot is indeed made of silver.

**Conclusion**

Measuring the density of precious metals using Archimedes’ Principle is a straightforward and effective method for verifying authenticity. It doesn’t require any special equipment and can be performed with simple tools you likely already have at home. This method, combined with other techniques such as measuring dimensions with a caliper, provides a robust approach to ensuring the quality and authenticity of your precious metal items.

**Note #1:** It is also possible to use a **Precious Metal Densimeter** which is more accurate and easy to implemet the density test.

**Note #2:** When mesuring density of jewlary make sure they are not hollow , (as the test can not be applied for hollow items).

**Note #3**: Density test alon can not guarantee autentication , but is a good indicator.

**Stay tuned for our next post, where we will delve into more advanced testing methods for precious metals. Until then, happy measuring!**

Ami Gur