The Boyle's Law apparatus has leaked

 I had a surprise with the Boyle's Law apparatus because the readings didn't match those I took a decade ago. Here it is on 180kPa and the air volume is 33cm^3. A decade ago, the volume was 22cm^3. The ideal gas equation is pV=nRT. pV is 180 x 33 = 5940. A decade ago pV = 3960. So nRT must be bigger. The room temperature won't have changed much and R is a constant. Hence the number of moles of gas must have increased. Air must have leaked into the apparatus.

But it still gives results that show that pV=constant (roughly). Below we get 160 x 38 = 6080.

And finally 100 x 58 = 5800. So pV is always around 5900. This is one way of illustrating Boyle's Law.