The Ultrapyc gas pycnometer (Anton Paar Ultrapyc 5000 Micro) can be used to measure the density of solid and semi-solid substances to determine the purity or porosity of samples. Samples with a volume of only 0.25 cm³ (but also larger samples of 1-3 cm³) can be measured with a maximum deviation from the accuracy of ~1%. The device is equipped with a balance and can be used on request.