Weight substances is determined by weighing. The basic unit of mass of the system is the kilogram (kg), kilogram is defined as the mass of 1 liter of water at a temperature of 3.98 ° C and atmospheric pressure. However, pressure is also defined by the kilogram.
When working with hand, pharmacy and technical weights, a set of weights. Weights are manufactured from stainless steel or brass. When weighing not use weights of several sets simultaneously. Fractional Weights weighing less than 1 g are made of thin brass or aluminum plate and have a different shape
Zero and the equilibrium position
Before each weighing, check to see if the weights are positioned horizontally using a spirit level or olovničky, which is part of the balance. Then check the zero of the scale. In this position, the tongue rocker unencumbered balances to zero. Digital scales are equipped with water level, which is located on the front of the field operator. After checking balances embarking own weighting, which is terminated when the mass of the substance equals the mass of the weights and the tab shows zero. This position is referred to as the equilibrium
Location weights is very important. Balance must be protected from dust and fumes of corrosive materials. Scales do not have to be near open windows or doors causing drafts or rapid temperature fluctuations Scales should also not be exposed to direct sunlight for záření.Nejlepší weight is equal to the solid surface and stable place. Particular attention is paid to the location of analytical balances. The balance room is necessary to maintain maximum cleanliness as dust weighing instrument very harmful.
For proper operation it is necessary to maintain a balance in absolutely clean. Most suffer from the scales. To clean the weights used dry cotton cloth, štěteček.Při weighing on an analytical balance must be all objects completely clean and dry. The balance must not weigh volatile substances in open containers. Depending on the nature of the substance to be weighed weighing using a watch glass, pan with lid or boat.
Weight substances determine a balance. Dear one of the basic and most important work in the laboratory and a pharmacy. The actual procedure varies depending on the chosen weights, the amount and nature of the substance to be weighed and weighed required accuracy.
Types of scales
Scales are divided into several groups based on their accuracy and capacity.
Capacity is the highest possible load at which the weight will keep the required technical measurement characteristics. Scales work on the principle of the lever and may be isosceles or unequal. The simplest isosceles scales are hand weights that were used previously.
Laboratory and technical scales
Laboratory and technical scales are accurate with equal weight, the rocker is in the middle. Pharmacy scales have aretaci.Technické scales from the pharmacy differs in that there is a lock. Laboratory and technical scales have a weighing capacity of up to 1000 g, 20 mg and sensitivity to them can weigh 0,01 g. Suitable for tare containers, such as direct weighing. Liquids or
Formulation scales or weighing scales have a weighing capacity of 50 g sensitivity 5 mg and 0,001 g. Used only for the weighing of powders, usually in small amounts, are not used to tare containers. For direct weighing powders is right bowl adapted to their rounded shape.
There are different types of digital scales that are different sensitivity and maximum load. Among digital scales can be included předvážky, precision digital scales and analytical balance. Accurate weighing scales allow quick substances. Předvážky are typically used to determine the approximate weight in order to work accurately, it must be preheated before starting work, ie. Weights that adapter is connected to an electrical outlet proudu.Váhu must be protected against the ingress of moisture and dust.
Analytical scales are very accurate and allow you to weigh with accuracy 0.1 to 0,001 mg. Dear exactly given by the initial weight. is very time consuming and requires carefulness to avoid contamination weighting material. The analytical balance is also not weigh volatiles in open containers, eg. Ammonia or acid.
Laboratory předvážky are used in pharmacies and laboratories for check-weighing or weighing mixtures.