Copper number

The term hydrocellulose has been assigned to the hydrolytic products intermediate between cellulose and n-glucose. When cellulose is subjected to the action of acid for even brief periods, there is a change in its tensile strength, copper number and viscosity. 

As shown experimentally by Piest [75], cotton which was subjected to various operations, e.g. bleaching, treatment with alkalis or acids, strong heating prior to nitration furnishes nitrocellulose solutions of low viscosity. At the same time an increase in the solubility of the nitrocotton was also observed. This is evidence that the cellulose molecules are shortened and their content of terminal group is increased. A certain proportion of hydrocellulose and oxycellulose may result. The total effect is to bring about an increase in the reductive properties of the cellulose, i.e. an increase of the copper number. 

Cotton Copper number Nitrogen content % Viscosity sec Solubility in alcohol %... 

Treatment of nitrocellulose Nitrogen content o/ /o Viscosity of ether-alcohol solution sec Solubility in 95% alcohol 0/ /o Copper number after denitration... 

In view of the increase of the copper number it may be concluded that the substance undergoes strong hydrolysis and oxidation in the course of the treatment with alkali. Operations of this kind should therefore be performed with great care, since the over intensive action of these reagents and the appreciable fall in viscosity that ensues cause the gel formed after evaporation of the solvent to become brittle. In recent times therefore stabilization boiling under pressure has been widely applied. 

No. Material for nitrating Cellulose content % Copper number Pentosans content % Lignin content % Fats, waxes content 0/ /o Ash content %... 

Was this your answer Copper (number 29), silver (number 47), and gold (number 79) are all in the same group in the periodic table (group 11), which suggests they should have similar—though not identical—physical and chemical properties. 

Copper Value (Copper Index or Copper Number) of Cellulose It represents the amt of Cu reduced from the cupric to cuprous state in alkaline sola by lOOg of cellulose (such as cotton). In case of cotton, it gives an indication as to whether any appreciable changes have taken place during purification proceduresjin case of woodpulp, it indicates the degree of purity. Accdg to Doree (Ref 4 pp 26 32-3)>normal cotton cellulose has copper values below 0.2 while sulfite pulp has value>2. The alpha-cellulose obtd from sulfite pulp had a value of 0,8... 

The presence of S02 caused additional loss in strength over that caused by light exposure alone. Using copper number and carboxyl content as measure of degradation it appeared that the properties of samples exposed to light and S02 differed from that of acid hydrolyzed counterparts which had suffered similar losses in strength. 

The so-called copper number is still the method of choice in the pulp and paper industry in process control, but sometimes also in the research lab. The reducing power of cellulose is measured by reaction with an alkaline Cun-salt under defined conditions, the formed Cu1 ions can be titrated after re-oxidation [82]. The underlying reaction mechanisms are still not entirely understood, neither are the types of oxidized structures recorded. However, even though the copper number is only a sum-parameter, the data of which cannot be directly linked to the quantity of a specific oxidized function, it remains a valuable parameter for control in a number of industrially relevant processes. 

Copper number (Unspecific) Reducing power Titration Only relative data, mechanism ill-defined [82]... 

Air pollutants can cause damage to rayons. Artificial weathering tests have indicated that as the strength of the rayon decreases, its fluidity and reducing power as determined by copper number increase, but the carboxyl content decreases (62). When these tests were made with air contaminated with 0.1 ppm sulfur dioxide, an additional loss in strength was found over that caused when the weathering tests were made in pure air (62). 

Several investigators have studied the effects of deacidification on paper. Flieder (7) evaluated several deacidification procedures using breaking length, fold, burst, tear, reflectance, opacity, pH, copper number, and ash as criteria of change. Accelerated aging for 72 h at 105 °C and for 4 h at 87°C and 60% relative humidity was employed as measures... 

When cotton is treated with very dilute solutions of hydrogen chloride in an aprotic solvent such as benzene it suffers severe degradation. This is because the small amount of hydrogen chloride in the solvent is redistributed in the water adsorbed on the cotton, forming a very concentrated aqueous solution of hydrochloric acid [454]. At low moisture contents, the sites of the consequent hydrolysis are near the ends of the cellulose chains. The relation between DP and copper number therefore differs from that for normal aqueous hydrolysis. However, as the moisture content of the cotton increases, the type of hydrocellulose produced approaches that found with aqueous systems. 

Cotton is frequently treated with hot alkali in the processes preparatory to dyeing, as well as in the preparation of pure cellulose for research purposes. In the now nearly obsolete process of kier boiling as much as 4% of its cellulose content might be lost as soluble products. The observations that the loss in weight of hydrocelluloses in alkali boiling is directly proportional to the copper number led to the suggestion that short-chain materials were detached from the reducing ends of the hydrocellulose chain molecules and passed into the solution [455]. This was later fully confirmed and the mechanism of the process elucidated [456 64]. 

JCP Specifications. The U.S. Congressional JCP has published six government paper-specification standards for permanent-record paper (32). These specifications were written in the tradition of cotton or linen fiber, high folding endurance, and high cellulose purity as indicated by high a-cellulose content and low copper number. 

Carboxyl content was determined by the magnesium-ion-exchange method (5). For chlorous acid-treated pulp, the carboxyl group concentration was found to be 14.8 meq/100 g for sheets reduced with SBH, the carboxyl group concentration was 3.4 meq/100 g. Neither had any significant aldehyde group content the copper number (6) of the chlorous acid sheets measured 0.9 meq/100 g that of the SBH sheets measured 0.3 meq/100 g. 

TAPPI Standard T430 os-75, Copper Number of Pulp, Paper, and Paper-board . 

Sample Description Initial Reflectance at 457 nm (%) Lignin Content (%) Initial Hot-l%-Alkali Solubility (%) Copper Number... 

Note Copper number is defined as the number of grams of metallic copper reduced from the cupric to cuprous state by 100 g of pulp fibers. 

Less reliable reducing end group methods include the copper number of Schwalbe, the silver number of G6tze and methods employing phenylhydrazine. The D.P. values obtained by these methods, however, are usually of about the same order of magnitude as those obtained by the method of Bergmann and Machemer. ... 

The reactivity of mercerized cotton is increased by about 1 / times at lower temperature in comparison to that of unmercerized cotton. The increased reactivity is not so marked when mercerization is carried out under tension. The reactivity ratio is generally referred to as the ratio of copper number of the mercerized to unmercerized samples. The increased reactivity increases dye absorption, moisture sorption and chemical reaction, but at the same time it also accelerates the reaction with acids and oxidising agents and is susceptible to degradation. 

Figure 12-8. Effect of pH of hypochlorite solutions on the copper number and methylene blue absorption of oxycellulose [29].

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