6. Property and Equipment

Major classes of property and equipment consisted of the following as of the dates presented below:

During the three and six month periods ended June 30, 2025 property and equipment depreciation expense was approximately $91,400 and $177,300, respectively. During the three and six month periods ended June 30, 2024 property and equipment depreciation expense was approximately $87,600 and $178,700, respectively.

During the three month period ended June 30, 2025, the Company disposed of property and equipment with historical cost of $118,800 and accumulated depreciation of $110,600 and recognized a loss on disposal of property and equipment of $8,200. During the six month period ended June 30, 2025, the Company disposed of property and equipment with historical cost of $775,000 and accumulated depreciation of $766,800 and recognized a loss on disposal of property and equipment of $8,200.

During the three month and six month period ended June 30, 2024, the Company disposed of fully depreciated property and equipment with historical cost and accumulated depreciation of approximately $571,600.

There were no changes in the estimated useful lives used to depreciate property and equipment during the three and six month periods ended June 30, 2025 and 2024.